gorillaz1031So far I'm definitely sure only small percentage of Latvia inhabitants know French. So you have a very small chance of being understood if you talk to someone in French on the street.
Like I wrote, most of younger people/youth should know English, at least they communicate at the basic level. Many people staying here have relative or friends in English-speaking countries, so at least they know couple of phrases

But it doesn't mean you could widely speak English in Latvia or have a good job just because you know English.
So, definitely you may have sort of difficulties in Latvia if you know just English, but it also depends on the area WHERE will you communicate. I'm mostly sure in the Old Riga restaurants and bars mostly every staff member knows English at least at the basic level. But this is not about Latvia in whole, for sure!