So I’m aware Triton day is the big gathering of incoming freshmen, but for many people, including myself, attending that day isn’t possible. So are there any other events, maybe even during the summer, that freshmen can attend to get a feel of the school and meet other freshmen?
Your college at UCSD will have a summer orientation. They do a good job.
You can also take a tour: http://admissions.ucsd.edu/tours/