This must be the worst hop-on hop-off bus service in the world! I've traveled to many places, and I have used many similar services. This is the most unreliable service I have ever encountered.
There are two routes advertised for this service. On route 1, the buses are supposed to come pass every 20 minutes. On route 2, more irregularly at more than one hour intervals.
A group of us (about 10) waited for 45 minutes outside Plaza St Martin today for the regular 20-minute interval route. No bus ever turned up during this time. Eventually people just walked away.
I paid full price at the adjacent ticket counter (Florida 1095) - but of course, they refused to provide a refund despite the service not being there. This is unforgivable, and leaves visitors with a poor impression on this otherwise beautiful city. [There are so many other excellent experiences - like the BA Free Walking Tour].
I just treat this as money thrown away, and put it down to one of those terrible experiences you encounter when you travel. Shame on you Buenos Aires Bus!