We loved GOR but traffic can be miserable on Saturday if it is a beach day (this was December) and if not then you will just drive farther on the highway. So I wouldn't try to fit too much into that day.

We did not hit the wineries here (not enough time) but you certainly could see quite a few on your own. However be very careful of how much you consume - we did see surprise sobriety checkpoints on the GOR where they were measuring BAC. You may be more familiar with those than we are in the states, where they post advance notice of the checkpoints and do field tests rather than breathalyzers.