Hey,
I live in Myrtle Beach and have been to Orlando, so thought I'd reply to this one too.
I don't recall you saying WHEN you were coming, but if it's in the summer, and especially on the weekend, I would advise you to make reservations somewhere. Surely you want to be on the oceanfront?
We have very few hotels left. Everything just about now is a condo-hotel, and most have minimum stays of 4 nights during the season. (June-Sept)
If you aren't making reservations, then I would absolutely say to plan it to get into Myrtle in the daylight hours. Depending on which way you are coming in, the traffic is not going to be that bad except around 5pm or anytime on a Friday after 5pm.
You'd be better off traffic-wise to drive an extra 15 minutes and come in on Highway 9, and stay in North Myrtle Beach. It's better up here anyway, and unless you plan to go to the Hard Rock Park or something on the south end, we've got the same restaurants, less traffic, and prettier, wider, beaches.
In case you didn't know, Myrtle Beach and North Myrtle Beach are 2 different cities, about 15 miles apart. Both have the same streets...there is a 1st through 53rd Ave North in both Myrtle Beach and North Myrtle. So be sure you know which you are going to.
If you come in on Hwy 501, you come directly into downtown Myrtle...but even then if it's not a weekend, you will be ok. You can also come in that way, and take one of our new bypasses (either Hwy 22 or Hwy 31) and pop over to North Myrtle from 501 before you get to the beach. Otherwise, go on till you see Hwy 9.
It's just pretty confusing for tourists with streets and all, so I would advise arriving in the daytime if it's your first time here. And if it's a holiday or weekend arrival, get reservations first...especially if you only stay a few days.
Jan