I know you're anxious to get her to be more than a friend, but I strongly urge you to keep that under wraps for the moment. Here's why...she is probably sad about leaving the guy and is probably making all kinds of "we can make it even long distance" promises. To make even the slightest move right now could make her get all defensive and protective of her relationship with the guy.
I wouldn't go back to a place you used to go....she remembers being with you, and you don't want the choice of place to feel like any kind of pressure to walk down memory lane. Keep the conversation on San Diego. You could, if it comes up naturally in conversation, ask how they're going to handle the distance.
Give her a month or two of trying to keep things going long distance before you make any kind of move. You want to give her time to come to the conclusion that long distance romances are not much fun. Keep your interactions fun and light. Stay on the SD topic, and all the things you're looking forward to , and how cool it is that you'll have each other to explore with or bounce things off of as you both get used to living there. Her reaction to that will help you gauge her level of potential interest in re-kindling your friendship.