So if you would need new friends, how traditions may be related to it?
Traditions are mostly for locals ;)
Anyway... I think most of national traditions are related to the bigger holidays:
- Christmas and the New Year celebration - I think it's the most important family holiday in Latvia
- International Women's Day - 8 March - men are supposed to buy lots of flowers and make gifts to women ;)
- The WWII Victory day on fascism - mostly, only Slavic/Russian-speaking part of Latvia celebrates this day on 9th May
- Ligo: 23-24 th June, The Summer Solstice night - everyone is supposed to drink beer, eat cheese, have a nice sex and find a fern flower
- September the 1st - the day when our children go to school

meaning the adults party as well
- Latvian independence day - November the 18th - mostly, only local Latvians celebrates it actively.
I think you may skip some of the political celebration days, and whatever is left, you may use in staying with your friends ;)