The last day is your problem. Fri-Mon rental prices out @$25 a day for a compact, without playing around with coupons/promo codes. The Mon-Tue part causes you not to get the "weekend" rate. If you are staying in PS, you may want to price out just a Mon-Tue rental ($46 on Avis! but Enterprise/Dollar/Budget are all $20ish for a weekday rental) and do an airport rental car swap. The PSP airport is tiny, so it's not too much of ahassle if you are in the neighborhood. If you aren't going to be near PSP, book something now just in case rates go higher, then keep shopping around. Rates are always in flux.