I was not sure if people waited more towards the 4th of July. And do you leave them up until Labor Day?
Pre Memorial Day sales has tons of patriotic decor and you see it up all at least a week before the holiday. As long as the outdoor decor stays clean and undamaged all the way thru Labor Day is more than appropriate.
My outdoor bunting and flags always go out the week before Memorial Day. Some years I keep everything up and some years I don't. Sometimes the weather here is too hard on the flags and I take them up and down for the Summer Holidays.