Enjoy that. We visited the Baltic five years back and, as we were in SPB for two days, got our own visas which enabled us to leave the ship alone.
Really enjoyed it, though a smattering of cyrillic is recomended (my mum came with us and did not get the visa – she enjoyed the ships tours).
We visited Petrodvorits (Peterhof) in the early morning, and enjoyed it while it was bereft of tourists. The ship tour, by contrast, took over an hour to get there in the afternoon (traffic congestion), and they had very little time there..