The port director at a POE near here informed me that I wouldn't be able to enter the U.S. as a visitor while my I-129F was pending. There's also a website that seems to indicate the same. I can't post the link yet, but here are the quotes that make me nervous:
"All persons traveling to the U.S. as visitors or students, Canadian or other nationality, under U.S. law are deemed to be intending immigrants and thus inadmissible for temporary purposes until they have an immigrant visa in hand."
"While intending immigrants may have and lawfully seek to exercise a dual intent to be a visitor or student now and an immigrant later, it is against U.S. law to enter the U.S. as a visitor or student with the intent to wait for or seek immigrant status while in the U.S."
If there's any doubt at all, I'd probably lean towards not trying it, as I don't need any more bad stuff on my record (in addition to my previously denied
TN Visa and visitor visa). Also, with the cost of airline tickets, it would suck to spend $600 only to be turned away while trying to get on board the plane.