Depends on what road you are on....I’ve been on highly maintained roads like the Mass Pike and NY Thruway [tolls] that are pretty clean - I’d steer clear of ones on poorly maintained highways.
I’ll stay off of them during messy winter days or when raining because it will spray the cars behind you.
I bet you a buck it’s illegal - just be careful of surroundings when you do it - everyone can hear it ;)
A nice leisurely glide over the rumble strips will move over the un-attentive - adjust time accordingly, if it’s a Green K-Car or whatnot - linger there more so they will wake up....lol
Only time I get on the rumble strip is when I am trying to put my headlights in some slow moving truckers mirror at night.