Figured this was covered by Marty keeping a close tab on the local police chatter.
It fits, but is still a stretch given the speed at which it all happened.
Even if someone called as soon as they approaches the house, that still leaves literally only 6 minutes and ten or so seconds for Marty to get from wherever he was to that street. Given that people outside were still trying to figure out if they were cops for the first minute or so, I would say the cops were probably called with about five minutes left, and even that's generous.
Considering that Rust went off in a boat that Marty couldn't follow and then took a car ride to a separate place, the odds of Marty being in the same area, let alone within a five minute drive are pretty darn low. Marty didn't know they were going to rob a stash house in some projects, which would've at least given him some idea of where to head towards. The way it played out though, they could've been literally anywhere that could be gotten to in the time between Rust riding off on the boat and his phone call. But even with the time necessary for the police to register the call then get it out on the radio and them have Marty identify that it was Rust and the bikers and get from where ever he was to that general area, he was still able to make it to Rust in 90 seconds.
Unless I missed some sort of police surveillance that was continuously on Ginger that would've clued Marty in on where to go before the robbery started, it's miraculous that he made it there when driving five minutes in any other direction would've made him late.
Ack I don't want to complain. I'm not complaining. It was awesome.
Edit: or he just knew where Ginger's house was, made a good guess, and followed them out of there, although I can't remember Rust ever talking about who "his guy" actually was to Marty.