The Rays local broadcast is Sun Sports (Fox Sports themed). I'm not sure if you are in their market, but if you aren't you can get "At-Bat" through MLB.com It is a little pricey, but it's worth it if you also like watching other teams.
You can buy a very good TV for $20.00 these days, Of course I mean a used TV, but used TV's these days outlive their owners. Most MLB teams have a station where you can watch almost all 162 games. So no, you don't need MLB.TV. WPB is in Miami territory, but still, many Florida fans prefer Tampa Bay because they are the envy of all other teams. So they must still be very popular in WPB.
