VFE,
I've flown out of Vero Beach for the last 2 years, so I'm in and out of MLB on a regular basis. I've always found the guys in the tower to be extremely friendly and professional. Daytona Approach, who control the airspace above MLB's class D upto 5000' are the same way aswell.
As far as traffic is concerned, there's quite a bit of "instructional" flying going on because FIT are based there and FSI like to go there for the ILS. Apart from that it's nowhere near as busy as Vero gets on occasion.
You'll have fun.