I've stayed at many hostels in PR, but Island Time has been my favorite. From the moment I walked in, Cory (the manager) made me feel right at home. The location is sweet - you are smack in a colorful neighborhood with a bar across the street and quick and easy access to the most reliable bust to Viejo San Juan. Good conversation was never lacking and the atmosphere was super chill, inviting, and relaxing. AND the personal fans for every bed keep it cool and the mosquitos far away! Love it!
The first time I stayed in OldSan Juan, I stayed at a hotel that cost $170/night. Who knew that RIGHT NEXT DOOR was the Fortaleza Guest House which costs a fraction of that! The rooms were clean, comfortable, and there was a nice kitchen with fully stocked utensils to do all of your cooking. The location is great, right in the heart of San Juan and easy access to most things you would like to see. This hostel has definitely more of a low-key and chill atmosphere.
Fun staff, very great and sociable atmosphere. Relaxed and friendly space. Perfect if you are traveling alone and want to meet folks and have things to do. Only major downside is a lot of Mosquitos.