My DS lives in St. Pete, and I fly into both MCO and TPA when I visit. I've never flown into PIE, as the service there is REALLY sparse. Driving to the beach from TPA normally takes about 45 minutes in traffic, unless there is a baseball game. Assuming that there are no traffic jams on 275 in Pinellas, the quickest way to St. Pete Beach is to stay on the highway all the way through downtown St. Pete, then take the Pinellas Bayway over to the barrier island. You'll cross the toll bridge right opposite the Don Cesar.
MOST of the time, the drive from MCO to St. Pete takes about 90 minutes if you take 417 all the way South until it dumps into I-4. Traffic does tend to build up just east of the TPA airport near downtown Tampa, but the real issue is random southbound backups that can happen right about halfway down I-4, usually a bit south of the I-75 interchange. That happens just because the volume of traffic between the two metro areas is more than the highway was designed to handle.
Once you make it to downtown St. Pete, it's normally about 15 minutes to SPB via the Bayway. That's a toll bridge; under $2 to cross. There is a free bridge on the north end of St. Pete via Pasadena Blvd, but that's a long stop-and-go drive via surface streets once yu leave 275, so unless Waze tells you there is traffic on the south end of St. Pete, the Bayway is faster.
What all that boils down to is that flying into MCO for a trip to the beach is not onerous if your flight times or money saving are beneficial. I often fly Frontier for visits, and the price savings makes the drive more than worth it. Also, due to a fee situation being levied at TPA to pay for construction, lately car rentals at MCO usually cost less, so it's best to check both prices before making a decision.
