It all depends on timing. Before Spring Break and/or Memorial Day, probably won't be overcrowded, but may still be busy. During the summer months, it could get crowded. Holidays or weather could also influence it.

Easiest way to check would be to see how the online tickets look, in terms of sold out time slots. There could still be plenty of walk up ticket sales that day, but it's a good initial indicator. Plan to go closer to 5 so that you have enough time before things start to close inside.

If you're a MD resident, there are discounts in the AM hours as well, though this time of year, there will be lots of school field trips in the building early on, so expect lots of screaming kids.