The tail lights are most likely like the sedan's; they don't have a butyl seal like the headlights, so you can't just open them by putting them in the oven.

most likely a seal for the bulbs that has rotted away and is letting in the condensation.

Your best bet is to take off the headlights and inspect the rubber seals for the bulbs.

 

Providing the condensation isn't due to a cracked lense, you can simply repair the headlight. You will have to use a dremel or small cutting wheel to the existing seal so you can remove the lense cover. Make sure not to touch or clean the inside of the lense because you may damage the UV protective layer or scratch it. Black silicone made by Permatex is one option for resealing it. Or a clear silicone adhesive will work. The following links shows how to open them up so you can reseal them.

http://my.is/forums/f221/diy-removing-blacking-out-tail-lights-396040/
http://my.is/forums/f221/diy-black-housed-taillights-lots-pics-432241/

Hope this helps..

edit; I knew someone would beat me Inspection of the socket seals is a good idea but your lense seal may be compromised. Worth it to check the sockets first as mentioned.

 

The harness for all the bulbs which includes the rubber seals is $24.91 on Sewell after our discount. So if you find the seals are dry rotted or cracked this would be ideal to replace and see if the condensation goes away.

81555-53040
REAR TAIL LAMP (TAILLIGHT) SOCKET AND WIRE SUB-ASSEMBLY (RIGHT / PASSENGER SIDE), SPORT CROSS ONLY - WAGON

2002 IS300: OEM Electrical (REAR COMBINATION TAIL LAMP) Replacement Parts

 

Thanks, guys. I guess I have multiple options!

The harness for all the bulbs which includes the rubber seals is $24.91 on Sewell after our discount. So if you find the seals are dry rotted or cracked this would be ideal to replace and see if the condensation goes away.

81555-53030
REAR TAIL LAMP (TAILLIGHT) SOCKET AND WIRE SUB-ASSEMBLY (RIGHT / PASSENGER SIDE), SEDAN ONLY

2002 IS300: OEM Electrical (REAR COMBINATION TAIL LAMP) Replacement Parts

@jasonm4: thanks for the link, very helpful, but just so this thread has the right information I'll note that I have a SportCross so here is my part:
81555-53040
REAR TAIL LAMP (TAILLIGHT) SOCKET AND WIRE SUB-ASSEMBLY (RIGHT / PASSENGER SIDE), SPORT CROSS ONLY - WAGON

 

If replacing lightbulb assembly doesn't work, I do have a passenger taillight, in the for sale section.

 

You're welcome and hopefully it's just the socket rubbers that are shot.

I should have known better that I was in the Sportcross forum:duh: I edited my Op.