How early should we get there? Is there a time frame for getting a good spot? (Are there good/bad spots?)

15-20 on weekdays, 30+ on weekends

Depends. On an opening night of a movie, hour ahead at least for a good spot. That gives you time to prepare and get your snacks there if you wish. The prices are a bit steep so plan accordingly.

We always like parking in the front row and so usually go about 20 minutes early.

I usually get there at the last minute and always get great spots weekends and weekdays