We used to layover in ONT - a short drive from home. I just asked the hotel if it would be OK to park in their lot. IT WAS! I parked there and took the hotel shuttle to the airport.
Just a $2.00 van driver tip and a note in the window of my car saying it's OK to park there per so-n-so is all it took. When we changed hotels, I did the same thing there too. It worked great - try it. It'll cost you about $12.00 a month for 3 commutes.