Someone can correct me if I'm wrong, but I'm 98% certain that it'll have barely any effect on the performance.

Another thing that may help is setting the gta_sa.exe priority on task manager to a higher rank. On my old computer, I raised it from
Normal to
Realtime and it boosted the fps by around 33% (I had that figure accuractly calculated as I had fraps running and made a comparison via calculation). However, depending on your computer configuration, it may have a noticeably negative effect on some other processes if you set it too high.