Depending on where you live, you need to have Location detection enabled in your Vita settings, as well as enter a WiFi area in a new neighborhood.
You're allowed to access 1 street smart per location per week, so you could just stick to your home location until you get 100 stars, or try going to public wifi locations like Starbucks, McDonald's, Best Buy, or whatever may be available in your region.
The maximum stars you can get per Street Smart is 9, getting 3 stars per game for 3 games, however the games increase in difficulty--with the first being an Easy game, then a Medium game, and finally a Hard game.
My personal goal was to shoot for at least 7 stars per Street Smart, so I wouldn't go too crazy over them. You can try as many times as you like within that 1 week period, so if you get 5 stars at first, you can keep trying to increase your total stars for that location.
If you'd like to manipulate your router's location, you can use SkyHook by checking out the other solution for this trophy (I don't want to copy his solution, I'd rather link it):Solution for Globe Trotter in Smart As (Vita)