I just picked up a decade box from there last week.
Right now due to COVID-19, walkins are not allowed. If you want to go in and poke around, you need to make an appointment, send an email to <surplus at ucsd.edu>, or you can call the number on the site and leave a message. They're open between between 1-2:30pm on Mondays, Wednesdays and Fridays, and they'll assign you a time in that block.
The guy showing me around also said that they were in the middle of migrating their website, and I found things on the site don't work as you expect, but keep poking at it and you should eventually get to find what you're looking for.