Some possible ideas (Pell being a proxy for unpreppiness):
University of Texas - Dallas: 33% Pell, in Dallas, but ~40% commuter, in Texas (family politics)
University of Hawaii - Manoa: 30% Pell, in Honolulu area, but ~50% commuter
San Francisco State University: 43% Pell, in San Francisco, but ~50% commuter
University of California - Santa Cruz: 39% Pell, in Santa Cruz beach town, but CS is mildly impacted (2.8 college GPA needed to enter)
Arizona State University - Tempe: 29% Pell, in Tempe (Phoenix area) (note: the other campuses like Downtown and Polytechnic are more for non-traditional students)