If you have to go somewhere in the...
If you have to go somewhere in the middle of the weekday, somebody coming to work might take your spot, but you can usually find another one somewhere else (maybe slightly farther away, but ‘far’ in Caltech terms is under a 10-minute walk). Speaking of which, the campus is pretty small; end to end, it’ll take you 10–15 minutes to walk at a leisurely pace.