54 Langeach Sros is one of my favorite beer gardens in the city but it's actually #15A!
Sary's Guesthouse is near the riverside, it's clean quiet and friendly but it's not going to blow you away. It's only about $20 a night though, and Sary is a wonderful guy.
There's a lot of nightlife on the riverside, but also on Street 51. Just depends on what sort of nightlife you enjoy!