There are a good amount of shops right on Calle Ocho, basically you just drive down the street and spot the shops/small factories. I went to the Padron's factory in January, but it was a little farther north. The only thing is that the Padron's factory in Miami is only boxing and packaging, so it would be a wise idea to miss it if you are pressed for time.
If you really need something, I still have a printable email I got that can give you some factories and cigar shops on Calle Ocho.