Can't recommend a pub for the football but a few pointers for Riga.
It is a fantastic city, one of the best City breaks I've done.
Some must dos :-
Go for the free walking tour of the city. Not free but you tip the guide at the end of it - about 5 Euros a head.
Go to the corner house, the HQ of the KGB when they were based in Riga. A harrowing experience.
Go to the museum of the occupation and get a guided tour. There's not a great lot to see but if you get the tour, the guided tour through the history is amazing.
Go to the top of the sky tower for a drink. Amazing views across the city.
If you have time, take a train out to Jarmala beach. The train costs about £3 return but it's the touristy resort on the Baltic Sea. Excellent bars and cafes in the town centre.
Enjoy Riga - I loved it.