It is useful to understand that although from 1940 to 1991 Latvia was a constituent republic of the USSR, the official language is Latvian. However, a significant minority (up to 40% nationwide and possibly just over 50% in the capital Riga) is Russian speaking. The majority of ethnic Latvians living in the city, not only those old enough to have attended school during Soviet times, can also speak and understand Russian. However, many prefer to converse in Latvian. English and also German are widely understood at places regularly visited by tourists and foreigners but you may be out of luck when leaving the city centre or visiting places off the beaten track.
Jelgava is in coast of river Lielupe. River Lielupe is connect to Baltic see.
You can rent taxi (if arrive from Riga or Riga airport).
There is few clubs/pubs.
Most popular are Tonuss - club, with several halls. Place with a lot of young people. Jelgavas Četri Balti Krekli - club where play only Latvian music