One of Mérida’s best hostels, Nómadas has mixed and women’s dorms as well as private rooms with bathroom. Guests have use of a fully equipped kitchen, as well as spotless showers, toilets and hand-laundry facilities. It even has free salsa, yoga, trova (troubadour-type folk music) and cooking classes, and an amazing pool out back that is always buzzing with a young party-friendly crowd.
The owner, Señor Raul, was one of the first 'contemporary' hosteliers in Mexico, and he knows his stuff. See the hostel's website for various tours available to nearby ruins.