^What BreifCasey said. Generally, no, you don't get a choice of which parking lot. But 95% of the time if you enter from Universal Hollywood Drive, you'll be sent to Jurassic Parking. But they also don't have as many parking booths or attendants.
Entering from Universal Studios Blvd 95% of the time will get you ET or CG, but they also usually have more parking booths open, especially in the morning.
Frankenstien parking, nowadays, is only for Preferred Parking... and if you decide to opt for that, at the Universal Hollywood Drive entrance, they just have you U-turn and head back for it with a pass. It's weird, but that's what they do. From Universal Studios Drive, they'll direct you to it.
One additional thing to note... should you want to leave the park and return later the same day, just show your pass from the morning and you don't have to repay. There's some good food off-property (Spitz, Little Toni's, Rodini Park, Miceli's--where the wait staff sings from time to time)