Trelew is a small town founded by settlers from Wales in the greater Puerto Madryn area. It is an unremarkable mid-size city. There is not much for tourists here (see things to do below), but may be a convenient stopover.
The airport in Trelew is served by Aerolinas Argentina 2-3 times a day as a stop-over from flights going to / leaving from Buenos Aires to El Calafate. Additionally, buses regularly arrive and depart the bus depot. It is roughly a 23 hour bus ride from Buenos Aires.
The bus station is fairly centrally located, to the east of Plaza Centenario on the corner of Lewis Jones & Urquiza. Two companies operate services to Buenos Aires (~20 hours, 1000 - 1400 AR$ depending on seat travel class Feb '15). El Pinguino operates to El Calafate (~22 hours, 1000 AR$ Feb '15). Trelew is on the main routes south to Rio Gallegos and onwards to Ushuaia. Connections to the west include Esquel.
The city is served by an extensive local bus service which besides providing transportation around the city also provides services to nearby Rawson and Gaiman. You will need to buy a electronic card (20 AR$ Feb '15) for the 13 AR$ (Feb '15) single fare to the Welsh colonial village of Gaiman unless you have enough coins to place in the machine on the bus.