You will find the GC alive on Marine Band, especially during summer! Lot of yachting along the ICW (Though they do talk more on Ham than Marine they do have to keep in contact with other traffic), lots of traffic into and out of the Port of Mobile, and all around the Florida coastlines! Lot of shrimpin/crabbin along the coast, and yes, you want the USCG LMR, and UHF nets in. Just remember that USCG does go fully encrypted when doing interdiction activities now on the LMR. And yes you do get some cruise line traffic (Carnival Fantasy), but its not as active as say NOLA or Miami. And once closer to FL, you can start hearing USN if they are doing exercises in the Gulf, or cruising to or from Pensacola NAS.... Busy areas for Commercial Craft: Biloxi/Gulfport, Mobile, NOLA, Pensacola, then further along the FL line.
Also, keep an weather eye open ya land lubber! Though Tropical fun is usually later in the season for the Gulf, sometimes you do get early blows.
On the AFRRN, most LE is full time E down there, as are a lot of the LE on other TRSs and conventional... Mobile is transitioning from the EDACS PV, to P25... Not sure just how much E they will run yet, but being AL and on the GC, a LOT wouldn't surprise me. And you're in crap shoot in FL for LE lol... Also remember they are NOT scanner mobile friendly in FL so much. If you are an Ham, keep that ticket in the open once in FL.