So just doing some rudimentary research on SAN flying for OO E175s:
United - SAN-LAX anywhere from 2 to 5 x per day on the E175 currently. There will be the occasional DEN and SFO depending on season.
Alaska: SAN to BOI, AUS, DAL, FAT, OMA, SLC, SMF, SJC, HDN.
Through DAL, Alaska E175s will fly to LGA, PDX, SJC, SAN, and DCA.
Delta: SAN-LAX right now 1 x per day, but by mid summer it'll be 4x per day. (Currently compass does 4 times but will be down to once per day). The switch happens 12 June.
According to Deltanet
Compass departures out of SAN:
May - 179
Jun - 124
Jul - 89
Skywest departures out of SAN (not counting CR7/9):
May - 31
Jun - 136
Jul - 199