Preparations are definitely picking up.

A caravan of arrivals for ASHLEE SIMPSON and PETE WENTZ's expected wedding is evident at the gates of at patriarch JOE SIMPSON's L.A. compound, the Associated Press reports.

V.I.P. shuttles and delivery vans -- some marked as belonging to celeb chef WOLFGANG PUCK -- are steadily being waved onto the premises by sentries in a guard tower, who've been telling guests arriving in their own vehicles to park elsewhere and hop aboard a shuttle!

Stay tuned, more details to come...