Yes, whatever you do, don't give the telephone agent a chance to bring up your reservation. They very well may document your record saying no same day standby. I have found in general (regardless of ticket rules) the airport agents will let you stand by for same day flights. However, I have not booked PriceLine for airline tickets. So as others have suggested, try your luck at the airport!

A couple more P/L air stories:

__My roommate was ticketed on P/L for a TWA JFK-BOS-JFK ticket. He was all done whatever he was doing in BOS one afternoon, and was scheduled to fly TW at 5AM the next morning. He went out to BOS, and tried to stand-by on the last flight of the night BOS-JFK. He told them he had nowhere to go in BOS. The TW agent told him that he could not travel a day earlier, and if he had nowhere to go, he could sleep on the floor of the airport.

__Another friend booked BOS-MIA-BOS on P/L via US. In CLT, she tried to change her return date. They had all the paperwork done, and actually swiped her credit card for the $75 fee. Then they said "oh its Priceline<" and would not change it. They said you had to go through P/L who of course will not make changes. They will only make changes if you have medical letter. If you have a medical related letter, they might make some kinds of changes. Still your change is on the same day so perhaps you won't have as much difficulty.