“Infamous” means famous in a bad way. It is related to the word “infamy.” Humorists have for a couple of centuries jokingly used the word in a positive sense, but the effectiveness of the joke depends on the listener knowing that this is a misuse of the term. Because this is a very old joke indeed you should stick to using “infamous” only of people like Hitler and Billy the Kid.
“Notorious” means the same thing as “infamous” and should also only be used in a negative sense.
“Notorious” means famous in a bad way, as in “Nero was notorious for giving long recitals of his tedious poetry.” Occasionally writers deliberately use it in a positive sense to suggest irony or wit, but this is a very feeble and tired device. Nothing admirable should be called “notorious.”
The same goes for “notoriety,” which also indicates a bad reputation.