Such a deal!
We had a Groupon for the Riverwalk Plaza. On winter break from my husband's teaching job in Detroit, we stayed at the Riverwalk Plaza four nights (with indoor parking and breakfast) for under $300. It's located right at the corner of the main riverwalk, a tad off the beaten path. It's conveniently located a 10 -minute walk from both La Villita and the Mercado. 
Riverwalk Plaza is an older hotel; that shows a little in the corridors, but the rooms are comfortable and the bathrooms are recently updated (they could use an extra shelf for two people's toiletries). The staff is pleasant and helpful: I called directly, rather than book online, because we were splitting our stay for a side trip to Austin and Hill Country -- no problem, they gave me two reservations, both at the Groupon price. The Groupon breakfast was sit-down, not buffet, and limited to two fixed menus, eggs and hashbrowns, or pancakes, and both were delicious. We ate one dinner at the in-house restaurant Bar-Salona, also well done, reasonably priced, and a served by a hunky waiter!
All in all, we got a great deal and were happy to spend our money at Biga and the Mercado instead of on a generic chain hotel.