So my family is flying in and we're driving down to San Diego the first weekend in October. I have been doing a little research here and there, but are there any unspoken/unwritten helpful tips from people who have been to the zoo? In particular, do they generally have plenty of wheelchairs to rent? My grandmother will need one and we're going to arrive at opening time, so I'm hoping that they are plentiful enough. Any advice would be great appreciated!