The prospect of being able to find someone that you could have some fun with on a party bus is a big part of what might make you want to go to a party bus in the first place at this current point in time, and you would be eager to think of ways in which you can make yourself attractive to the opposite sex. What you basically need to do without a shadow of a doubt when you are on a party bus is find some way in which you can end up indicating to the other person that you might want to have a conversation with them that could be somewhat on the more private side of things.
It can be hard to try to extract yourself from a party that involves a lot of people that are all talking at once, so if you find something on a party bus in San Diego that you find to be truly attractive one thing that you can do to try and get some private time with them would be to ask them if they want to go and have a smoke with you. The person that you are speaking to could very well be interested in this, and if they say yes to this kind of thing then the end result would be the two of you really hitting it off.
This is not going guarantee that the other person will be down for anything romantic or sexual with you, but it will at the very least get your food in the door which is an essential first step for you to take.