[Goldia]

With EMH the first 30 to 60 minutes will be busy with non resort guests as anyone can join a ride queue upto the closing time of the park. So if MK closes at 10pm, then as a non deluxe guest I could join the queue at 9.59 and 59 seconds. After the closing time they used to scan magic bands before entry to the line to check you were an onsite guest. It didn't take long for this. Non resort guests are allowed to stay within parks and shops after park close, in fact many people will opt for this as a strategy to avoid packed transport back to their car.

So, it will take a little while for it to feel less busy, but having said all that Disney are known to inflate posted wait times so while it may say 45 minutes wait for Space Mountain it may be more like a 20 minute wait. You've just got to chance it really and some times you will get lucky.