Sorry about the late reply, Sasha!
I am sure I wrote a reply to a similar topic somewhere else and I even wrote a whole article on my experience which was never published and the forum answer must have been deleted.
The short answer is that basically anybody (Mercosur or not, I am not) can answer a bank account in Uruguay.
The long answer is that you need to bring information, as much as possible. Most important is a proof of the source of funds, both for the monthly receipts and the balance. In the past Argentinians had brought much black money to Uruguay. This is not wanted anymore.Â
It helped me that I had two contacts in Uruguay that I could name and an address even though it may not be a permanent one.Â
Many bank accounts are expensive here (therefore many Uruguayos do not have one), but if you deposit money some banks give interesting interest rates, making up for the banking fees. There are many options depending on what you want to use the account for.
Hope this helps.
Armin