Try the bars in Old Riga. You could try Balzama bars (http://www.balzamabars.lv/, but be careful ordering cocktails with Balzams), Thanks God its Friday (http://www.piektdiena.lv/), Skyline bar (http://www.revalhotels.com/en/Hotels/Latvia-Riga/Reval-Hotel-Latvija/Leisure/Entertainment-and-nightlife/Skyline-Bar), Casablanca bar - also in old town (check http://www.tripwiser.com/trip_restaurant-Casablanca_Riga_Latvia?itiNodeId=8a8c80fe158806790115886e91a13e6d&eType=restaurant). Enjoy!

at the old riga. There are lot's of small pubs and bars. And the prices are low

Try Tequila Boom for a nice mexican taste.

Some nice bars and places where better not to go you can check here: http://friendinriga.blogspot.com/2011/01/where-locals-have-fun.html and here: http://friendinriga.blogspot.com/2011/07/where-locals-have-fun-ii-shot-leningrad.html

Old city is full with bars and pubs, just pick the style you whant, then i can try to help you

Terrace Riga Balzama bars Skyline Alberta hotels' bar Gutenbergs bar Paldies dievam piektdiena ir klat (Thanks God its Friday)

Cuba cafe, Pulkvedis, Kalku varti, Shot cafe, Mojo cafe, Piens, Andrejsala (see event list),