There are organized drags from the ASDRA this weekend in Yuma. Here are some directions to the dragstrip that I wrote up for the GD.com drags we had there last year:
http://yumaduners.com/jth_upload/drags_directions.jpgIf it's your first time in the big dunes Gordon's is probably a safer bet - but be sure to go with a group! It's a much larger area and very easy to get lost. A good tip is to stop on the ridge between the flats and the dunes and get a feeling for the horizon before you head into the big dunes. There are several towers with blinking lights on top which are visible from almost anywhere in the south dunes and you can usually use them to find your way back. One is near the bridge over the canal at the entrance to the flats, one is by Pair-a-dice and one is a little further east. Once you learn which is which it's easy to navigate by looking for them out in the distance when you get to a tall hill.
If all else fails you can use the go in one direction trick:
North Edge: Patton Valley and closures. If you see the red stakes you're at the closures. Just follow the stakes to the west to find the sand highway.
West Edge: Sand Highway follow it south to Dune Buggy flats
East Edge: Dunes turn into desert follow edge of dunes south to highway and pickup ridge to get back to camp easily.
South Edge: Canal - don't go over the ridge too fast

Buttercup has more technical dunes (smaller bowls with more razorbacks) so if you like to jump it's a better bet. Apparently there are new border markers up so it's a lot harder to get lost at Buttercup unless you run into a sandstorm and can't see 10 feet in front of you! There are power lines that run over the camp area and you can usually spot them from anywhere in the first finger of dunes to find your way back. But since Buttercup is smaller you can always just keep going in one direction and eventually you'll find your way:
West edge - Dunes run out - then go north following the edge of the dunes to find the highway.
East edge - Canal, just follow it north to the highway and back to camp.
South Edge - Mexico, if you see farmland you went WAY too far and are deep in Mexico. Just go north until you get back. But hopefully with the new markers it's easy to spot the border.
North Edge - Highway, tough to miss!