Anna, the problem is here in Russia we have very long winter holidays — from Jan, 1 till Jan, 8. That’s why the schedule of regular salsa discos will be changed for sure. So now nobody can answer you on your questions. I’d recommend you two things (both for your Moscow and St. Petersburg threads): 1) ask our salsa-guides when you will be already in Russia:
www.mambotribe.org/guides/ ; 2) ask people here one more time more to the point.