Street legal? Ish. The week of EJS you'll see full tube buggy's, UTV's, U4 cars, etc. driving on the street. Do you have a license plate? Don't drive like an ass and you'll be fine. You know Horus's ZJ buggy, he was all over town every day in it with no questions asked.
Weather? As stated, can vary widely. It's later in the spring this year but can still be chilly in the mornings. Last year was similar timing, we had a dusting of snow one morning but 65* by the afternoon. I think I did everyday in shorts, shirt and hoodie.
We'll generally make it to to Salt Lake City or Provo in one good 13-14 hour stretch, get a hotel, and drive the last 5-6 hours to Moab in the morning to get there early in the day, set up in our condo, grocery shopping, and ready to go.
The key to EJS is knowing where/when the official "RR4W" runs are so you can avoid them. If they're running Moab Rim and Hells Revenge, we go to Pritchett. If they're running Pritchett and Kane Creek, we run Hells Revenge, etc. Their permit grants them exclusive rights to the trails whichever day they are running each particular trail. It's easy enough to figure out though, the schedule is published.
We're staying in Rim Village condos this year. See 'ya there!