I have not been in Riga but they say that now it is quite comfortable city for the Russian-speakers in common life. Riga is known to have big number of Russian native speakers. There are also many tourists from Russia. There is political pressure to learn Latvian to locals who have official positions and necessary to obtain Latvian citizenship, but that will not bother you as a student/tourist. Anyway you will be immediately recognized as a "far" foreigner by your accent and any kind of possible rivalry will not touch you.