Buy a good handgun. No need to get crazy on gun or cost. $3-400 will get a good one. Get training. Conceal carry permits in Cali? Get one if you can, but take it either way. How does bf feel about that?
Extra gas...fill up every time you can.
A bag of good weed.
A cable & lock to secure the bikes to a post or tree.
Make sure bikes are in good shape...tires, chain, brakes, etc.