I've successfully driven all the way from Napa Valley, CA to Panama City, Panama. Though my original plan was to ship my car to Cartagena, Colombia, I decided instead to sell my car in Panama City and buy a bicycle or motorcycle in Colombia.
It took me 8 days to sell my 1999 Toyota 4Runner in Panama City. I posted it on the following websites:
The third one (below) is very popular in central/south america (the site is in Spanish) and costs $14.98 to list you car for 60 days with 18 photos & a video. All the emails I received from this site were in Spanish so speaking some Spanish is very helpful.
I ended up selling it on Craigslist to a Costa Rican guy who lives in Panama City, Panama and buys/sells cars for a living. I was originally asking $4500 but soon lowered it once I learned how high the import taxes are for foreign cars, which you can see here:
Panama Vehicle Import Taxes
For example, the import taxes for selling a $3,000 car would be around $1,700...a lot. I did sell my car for $3,000 cash and the process was quite easy. I gave the buyer 4 copies of my passport photo page & 4 copies of the page with my entry stamp into Panama. The buyer also took all of my paperwork (Panama vehicle import paperwork, Panama insurance and original California title, which I signed over to him) and gave me a stack of cash...transaction completed. I didn't have to go to any office or do any paperwork.
So, what do you do with a big chunk of cash while in Panama City? Get it into a bank as fast as possible! I went to Western Union the next day (yes, walking through Panama City with $3K in my backpack made me a little nervous), gave them all the cash, and they transferred the money into my AmEx savings account. I just needed the account # and a photo ID (license or passport). The transfer is supposed to take only one day and it cost $16.05 for the transfer.
Now I am car-less and even more free. Off to Colombia via the San Blas islands...