Tumbes is the capital of the Department of the same name in the Region Grau.
National buses run along the Panamerican Highway from Lima to Tumbes & some to the frontier with Ecuador. There are kombis along the coast to neighbouring towns, & frequent buses along the Panamerican Highway from Lima to Chimbote, Huaraz, Trujillo, Chiclayo, Cajamarca, Chachapoyas, Piura, Mancora & Tumbes.
There are kombis to beach resorts, & colectivos to the frontier. Customs & immigration are several kilometres inside Peru & Ecuador so make sure it is understood that colectivo/kombi/taxis wait while formalities are concluded, & they do not drive off with your belongings on any unexpected diversions. International buses are a safer means of crossing the frontier. Beware of false currency exchange.
White sand beaches, mangroves, Tumbes River & National Parks like Amotape. The Manglares are a series of swamplike everglade type islands in the shallow water. You can visit a small crocodile zoo, where they are trying to continue to grow the local breed.
Observe the beautiful Mosaic's in the town, including a 20' 3-D mosaic of Jesus ascension into heaven. Other ones can be found across the various plazas.
Go for a walk along the Malecon, the walkway along the river.
Get out to the beaches in Aguas Verdes, or Puento Pizarro to see the Manglares, or eat lunch on a small island only reachable by boat. Note that booking tours to these areas is easier and less expensive from Mancora. Tours from Tumbes are not common and may require booking a private tour.
Seafood is of course plentiful and affordable. There are many Chifa's, Chinese food with a Peruvian flavor, located on Feijoo street. Many delicious dessert shops are located in the market street.
Hotel Costa Del Sol chain, which maintains facilities along the north coast and in Lima, has one in the main plaza in Tumbes. Cheapest room runs about $90, or 270 soles.
Hotel Feijoo is a little more cheaper, but still of good quality, located on convenient Feijoo street with many chinese eateries and shops.
Tumbes is not a dangerous city at all, but it is indeed a place of many scams run by mixed ecuatorian/peruvian gangs, with the complicity of the frontier police and some bus companies.
Tumbes is a horrible town, but the border crossing has changed. There is a brand new nice building where you check out of Peru and into Ecuador in the same building. You no longer check out of Peru and have to taxi to the Ecuador office. You literally get stamped out of Peru, step to your right, and get stamped into Ecuador.
The border crossing is more confusing than intimidating or scary. Ignore offers for help. Police presence is strong and it seems unlikely one would get into any trouble crossing in daylight.
In february 2012, 4 argentinians were caught by "taxi drivers" waiting for tourists at the Emtrafesa bus terminal in Tumbes. They were told that Tumbes was a very dangerous city, that they shouldn't get out to the street if they didn't want to get robbed inmediately, and that a taxi to the frontier was the only safe way. The argentinians knew about the CIFA buses, but since the price offered by the taxi drivers was much cheaper, they got in. They were driven to a fake police control outside Tumbes and were forced to pay 100$ each, after which they were driven to the true peruvian border control, in which of course you don't have to pay.
These things happened inside the Emtrafesa bus company. One of the hostess was trying to tell the guys, by mimics, not to believe the "taxi drivers", which means that she and the whole bus company knew about these gangs.
Another possibility is that they don't pretend to be taxi drivers, but rather "agents" of the CIFA bus company that are there to take passengers to the CIFA terminal as a free service, avoiding them the infernal dangers of Tumbes. In that case, they will show you a very sketchy dossier that tries to look like CIFA "official stuff". Don't believe a word. The "agents" may provide a story that the border is going to be closed for several days due to protests starting the following day, so the border needs to be crossed as soon as possible.
Even within gated private bus terminals, "soft" scams mean taxis are best avoided. Inside Cruz del Sur's terminal there is a fixed rate list and drivers presumably authorized by Cruz del Sur, wearing badges and within the terminal. There are a few elements to this con. One of the drivers, waring a Cruz del Sur badge, will ask for your ticket to unload your luggage. He will take your luggage ticket and claim you don't have one for your luggage. It'll all be ok because he is the one handling your luggage and taking it to his taxi. Next, his friend will join you in the backseat, as they both talk up the mark (you) to make you feel more comfortable. From there it is a laundry list of scams . . there is a fee at the border, you must take a taxi because the border crossing is dangerous, buy a direct ticket to Quito for "only" $65 (price across the border: $12), etc. At last stop when finally demanding to leave the taxi in Agua Verdes, they may attempt to move your luggage to a new taxi to take your across to Ecuador (presumably for a high rate).
The advice is: never, by any reason, get into a taxi in Tumbes! Use buses or combis instead.
The cheapest way to get to the frontier is by combi. Combis leave when they get full from the corner of Abad Puell with Simón Bolívar, ask anybody at the main street to find them. If you get to the Emtrafesa bus terminal, you're just a corner away from the combis. They will let you off at the peruvian immigration control, where you'll have to get your passport stamped. After that you'll have to make your way to the ecuatorian immigration, which is some kilometers away. If you're around the peruvian border control between 9 and 10 a.m. you'll probably see some transnational buses (Rutas de América, Ormeño, etc.) waiting for their passengers to get their passports stamped: it is not a bad idea to talk to the driver to see if you can join the group until Guayaquil for some dollars. Otherwise, remember: be EXTREMELY careful with taxis around this frontier.
A much easier and safe way, but also much more expensive, is to take a direct bus from Tumbes to Guayaquil, that will wait for you in both immigration offices. Ormeño (Lima to Guayaquil daily & Quito weekly), CIFA (Tumbes to Machala, Guayaquil in Ecuador) & Transportes Loja (Piura to Machala), have international buses to Ecuador. Tepsa runs buses to and from Lima for about $31 or 93 soles. Although Tumbes is has a larger population than Mancora, busses run more frequently from Mancora to Ecuador than from Tumbes, and those busses do not stop in Tumbes.
Be careful not to get scammed by taxi drivers telling you that the Cifa terminal is closed and that you need to take a taxi to the border. The Cifa terminal used to be at 540 Av Tumbes as mentioned in the Lonely Planet guidebook. It has since moved down the street, somewhere in the 900s on Av Tumbes. A taxi driver scammed 20 soles out of me by showing me old information that said the terminal was at 540. The terminal is signed as Cial, but it is also Cifa International.
There are kombis along the coast to neighbouring beach resorts, & national buses run frequently along the Panamerican Highway from the frontier with Ecuador & Tumbes to Mancora, Piura, Chiclayo & Trujillo, (for Huaraz, Cajamarca & Chachapoyas), Chimbote (for Huaraz),& Lima.
The CIFA terminal is located sort of outside town and you will need a moto taxi to get to the center of Tumbes if you want to catch the Cruz Del Sur bus to Lima. The moto taxi should cost you $1. Another option to get to Lima is to book a cheap flight. Peruvian airlines has flights to Lima at 3pm and costs around $95 one way. There is a travel agency next to the Cruz Del Sur terminal that can book a flight at short notice. The airport is located a fair bit (15 mins) away and costs 20 soles or $7 so keep this in mind! The flight will save you about 20 hours on a bus!