(FORTUNE Magazine) - There's a long line of mayors hankering to get their cities wireless broadband. Garry Betty knows how to give them what they want. EarthLink (Research), the nation's biggest independent ISP, is rolling out wireless service in Philadelphia and Anaheim and just landed its splashiest deal yet - teaming with Google (Research) to make all of San Francisco a Wi-Fi hot spot.

Residents will get their Wi-Fi free with ads or pay roughly $20 a month for an ad-free, faster connection. Betty chatted with FORTUNE about his company's plans.

When will these cities go wireless?

The first 15 square miles in Philadelphia will be ready in July, and it'll take us to the end of the first quarter of next year to build out the rest. In Anaheim we're going to have ten square miles up and running April 20. And in San Francisco we have to negotiate a definitive agreement first.

How did EarthLink team up with Google?

We've been a partner of Google's for four years. Google only has three engineers working on Wi-Fi. CEO Eric Schmidt laughingly told me in a meeting that the best hires they ever did was when they hired those three Wi-Fi engineers and put out a press release. The market cap went up $10 billion.

It was never their intention to provide these services generically around the country. Another agreement Google has agreed to do with us, in a city to be named, is free local search. So instead of generic free low-speed Net access where you can do anything, it would be like a walled local garden. Let's say it's Philly, and you want to find out what the pizza place near your house was. You could get on our Wi-Fi network free and get access to phone, location, name. But you couldn't do e-mail, you couldn't go on the Web.

Can municipal Wi-Fi change lives?

If you take advantage of it, it can. Some people don't want to be that connected. All you can do is provide alternatives that make it easy, and make it as painless as possible for those people who are reaching to pay 50 bucks a month for Internet. It's not a panacea. It's not going to solve all the problems of the world. But it does help provide alternatives that people otherwise wouldn't have. We don't think this is going to compete against cable, which is still faster. What we want to do is offer something that's entry-level.

There's a perception that someone's going to come into a city and give away wireless Internet free. They're not. We're in this to make money. Yes, it's inexpensive. We're making the barriers very low. But make no mistake. This is a for-profit enterprise. We won't do a deal where we don't think we have a good shot at making a return.

Ultimately we don't think the free model works. But if it's gonna work, it's gonna work in a place like San Francisco because the household density is four times greater than the average. With the lower operating costs, you might be able to get away with it.