"Are there any cameras that show the the McArthur Causeway (836) or the 195 so that you can pick the best way on or off of the Beach?"
Yes, th Miami Hearld has a nice webcam that points east. On weekends, or during Season, you'd be able to see if the traffic is backed up going to South Beach.
Here is a link to most every webcam in Miami - http://www.miamibeach411.com/planner/mwtp-webcams.htm
If you know of any others, drop a comment.