Thanks for all the info guys.
Richie7, when is the next event you plan on attending? (mailbox is full)
Will I really need to alter the car (roll bar) just for a few track days?
Most groups that know what they are doing would require, for a convertible, a rollbar that passes the broomstick test (as I describe above), a helmet that meets their standards (probably SA2005 or later), proper clothing, and arm restraints. Check with the group before you sign up. No point driving to the track only to find out you fail tech inspection because of lack of rollbar, proper helmet, proper clothing (usually cotton long sleeve shirt and long pants) or arm restraints. Most groups also would require the same type of restraints for the driver and instructor. In other words if you have 5 or 6 points for the driver you must have the same for the instructor.
Of course I think you would be nuts to hit the track for the first time in convertible without a rollbar. Is your life really worth so little? When you have a rollbar installed and you remove the OEM hoops you'll know why depending on them for your life is a stupid idea. They are thin walled tubing (possibly aluminum) that would collapse if you rolled. While rolling the car is not common (thankfully) I have seen it more times than I care to think about.
Other things to do before hitting the track include:
1) Download a track map and video (ideally of a suitably powerful car, a Miata will not necessarily drive the same line as a Viper). Most track websites have maps and Youtube has video on just about every track. Make sure that the video is for the track configuration you will run, many tracks have multiple configurations. Watch the video a bunch of times so that you can learn the track somewhat before you get there.
2) Bleed your brakes using Motul 600 Dot 4 or equivilant fluid.
3) Check brake pads to make sure you have a lot of pad left. Take new pads as insurance, some tracks are tough on brakes. Two track days could wipe your pads.
4) If you can afford it buy racing brake pads to replace the stock pads. They stop better, don't fade, and will last longer on the track. I use Raybestos ST 43 or 44.
5) Bleed clutch using Motul 600 Dot 4 or equivilant fluid. Stock fluid boils and you can lose you're clutch. Happened to both my Gen 4s and to a bunch of other folks.
6) Check tires for wear and pressure. You might want to increase pressure from stock slightly (like to 31 or 32). I find if I go higher I find I lose traction.
7) Grease suspension.
8) If your car has 10K miles or so change differential fluid.
9) Change/check oil.