angler - Let me first start with a disclaimer, it's been since '02 that i lived in miami, so things may have changed; but when i live in miami these were some of my shore/wade haunts:
Try the jetty on the south side of the bridge (A1A) at Haulover Park ( Bal Harbour ). There is free parking during the day but at night they WILL tow... if you are night snooking you'll have to actually park in Haulover park near where the head boats go out (north side of bridge) and walk across the bridge to get to it. Walk the seawall along the condos to get out onto the Jetty. Its a bit of a hike 1/4 - 1/2 mile but can be well worth it, much more fun when you have two people, so you can the drop gear at the foot of the jetty and have a lighter walk to the fishing.
Also, used to be able to get onto the beach/grass flats on either side of the virginia key / key biscane brige. On the key biscane side park in the park (again where the head boats dock) at the foot of the bridge and wade on out... i think the beach on the north side of the causwaythere is restricted access so stay out past mean high tide line (which i belive is the legal demarcation between state property and private property). On the virginia key side you need to park (if it is still legal) in one of the pull outs off of Arthur Lamb Rd (the road is on the left near the sea aquarium as you are headed towards key biscane). If you are not allowed to park there, you can always try the fishing pier under the bridge. That pass used to be a good snooking spot. Remeber if its not legal i didn't suggest it!
On an aside, at the end of Arthur Lamb Rd there is a funky little dive of a bar for a cold beer after fishing where you can also buy bait shrimp by the pound.
Not sure about catching quality snook, but another good wade option is Matheson Hammock Park off of Old Cutler Road (just north of where Old Cutler intersects with Red Road). Access to miles of lush grass flats there.
Hope this helps. I'd check out the night fishing at Haulover first if snook is what you are after. Good luck.