Haraz Mountains are a region in Yemen
Haraz is an area named after the mountains which run through it and is home to some of the best qat and coffee in Yemen. For the tourist, outside of Manakha and Al Hajjerah, there are not too many places to go on your own (due lack of facilities and language barriers). It is fantastic for hiking but you should have a guide to make it easier travelling through the villages. It is one of the most conservative areas but offers some if the best hospitality and spectaclar views.
Manakha is the main city in the Haraz mountains and was an ancient stronghold. It is perched on a mountain-side overlooking the valley which leads to Hodeidah on one side and the mountains leading to Sana'a on the other. Most visitors are western tourists or Ismailis going to one of their pilgrimage sites behind the city. It is a "city" in relation to the rest of the villages in the region, but by western standards is definitely a village. Mahweet is a northern city in the mountain range, but Manakha has more to offer for visitors and is easier to get to.
Because of its conservative nature, a guide is really recommended in the area unless you are really experienced in Yemen and its culture. It is one of the most beautiful areas in Yemen and worth the visit, but be aware of how easily westerners can offend people (mostly by accident) and how that affects the visitors that come after them.
Arabic is the language, but outside of the Manakha area the dialect gets very thick and seeems almost like a new language. For this reason, unless you are very fluent you really should have a guide with you.
From Sana'a you can go by bus, taxi or private car to Manakha and from there set up your trip. To go by bus you would take the bus to Hodeidah and get off in Al Mughraba and take a taxi to Manakha from there. Taxis leave from Bab Al Yemen or from 'Aser.
See the performance at the Al Hajjerah Tourist Hotel in Manakha. They serve the best meal in the area (a full traditional Yemeni meal with Hareesh, Saltah and Bint Assahan as the highlight, as well as some other dishes)and after your lunch a local musician comes to sing and Abdullah Al 'Agel (the owner) and his sons come out and dance. They are famous in the area for their dancing and hospitality.