Watermelon and melons in genetal are a stretch in most of the inner bay area. They really prefer spots where it gets into the 80's and 90's in summer. If you can muster a really warm spot, go for it. As for the other more typical warm season crops, careful watering is a bigger concern. You can also start cool season veggies in Sept/October. You can even find blueberry shrubs or fruit trees right now, which you could hold in pots until the move; A dwarf Meyer lemon would make a great first purchase.