I love the Posada Ruiz 2. It is the best of the very cheap hotels in Antigua. Antigua has a very wide range of hotels in price and quality, ranging from $2 US to $500 US. per night. Posada Ruiz 2 is about 4 US dollars but it is the best of the hotels in the under $10 price range. They have 3 hot water showers that are cleaned in the morning and afternoon, and they change the sheets every day. I'd advice you to get a double room even if you are alone as it is only an extra dollar.
The workers are very diligent and very nice (especially Gloria and Maria, the two indigenous sisters). And the other guests are mostly well-informed european backpackers who are staying for a week or two on their way through central america.