We found this place in Lonely Planet & Rough Guides, had a lovely 3 night stay. We had the dorm to ourselves, it was simple & clean, with a huge bathroom & a huge balcony, which we enjoyed hanging out in. The hot shower had excellent water pressure, which is always a plus for me. It's located outside the city centre, we felt very safe here & comfortable walking out in the evening for dinner. Downtown Santa Ana is a 20 minute walk away or take buses 51F or C.
The rooms are on the 2nd floor, there's a restaurant on the first floor - apparently its one of only a handful in town, we didn't eat there but it looked like a good menu if you feel like treating yourself. There's a wonderful garden outside, which felt like an oasis, my favourite part of our whole stay in Santa Ana. There's a professional coffee machine you can use as well as the restaurant kitchen (there are 2 ovens). The wifi was very strong in the dorm & throughout the hostel.
Casa Frolaz is a great reflection of its owner, Francisco. He's very friendly, ever-smiling & always had time to chat. He offered us advice of places to visit & eat, as well as bus connections to the Volcano park. We felt very comfortable here, a home away from home!