There is a friendly regional airport in San Luis Obispo (airport code = SBP). It’s at the other end of town from Cal Poly, maybe 5 miles away. It currently connects to SFO and LAX (United) and to PHX (American), with 3-4 flights per day to each of these hubs. They are scheduled to add flights to SEA (Alaska) in April.
So to get to Cal Poly, you would fly to SFO, LAX, or PHX, then add a short connecting flight to SBP. Obviously this is more hassle and expense than getting to a college near a major airport, but it shouldn’t be a deal-breaker.