Just wanted to share an updated story about my visit to the migraciones office:
After a few days trips to Colonia fell through I decided to take my chances in line at the immigration office for my visa renewal. Yesterday (first attempt), I arrived at 10 am and was told all the numbers had been given out for the day and I would have to come back tomorrow(today).
Today I arrived promptly at 7:30am and went to the prorrogas line. I was 4th in line at the time and after about 20 minutes of starting and restarting the computer they finally got the line moving. When I got to the front I said what I was there for and the 2 guys and 1 girl there said I could not renew my visa there. Now I don't speak perfect castellano by any means but we all understood eachother. We went back and forth for a few minutes making sure we were on the same page and I even went into "there are 3 ways to do this: leave the country, pay the fine, or come here." But I was repeatedly told that was not an option. There was no mention of an appt, etc. only that I must pay the multa(fee/tax/ticket) upon leaving. Which is now by the way 300 pesos instead of 50.
I am almost positive this isn't really the case as someone here posted they did it just last week... but after trying to ask several people and getting the multa related response I couldn't face standing in the by this point several hour long information line only to have no numbers left yet again.....
This is not a rant, just sharing my story, I should have done something about it earlier....I guess Ill have to pay the multa after all...too bad- good luck to everyone else though!
Also, if you do go (hopefully on a day with better informed employees?) this is a useful link I found explaining exactly what needs to be done: