I've been a green card holder for two years. I just married my girlfriend from Romania. She was in the U.S. on a visitor's visa, which expired after we got married. I sent an I-130 visa petition to the immigration service for her, but got a letter saying it will take 180 to 760 days for them to process it. Is her stay in the U.S. legal while she waits for this?
We've got some bad news, and then more bad news on top of that. That 180- to 760-day time estimate isn't the length of time it will take for your wife to get a green card; it's the length of time that the U.S. Citizenship and Immigration Services or USCIS (formerly called INS) Service Center will take to approve the visa petition. That visa petition serves only to put your wife on a green card waiting list in category "2A." And the average wait for a green card as a 2A is usually between two and five years.
It's nothing personal, the government is simply swamped with applications. These delays are a normal but horrible part of the immigration process. For more on that, see How Long Is the Wait for Your Priority Date to Become Current?
In the meantime, your wife's entire stay in the U.S. is illegal now that her visa has run out. Now, she might be thinking, "Okay, I'm willing to take a chance and stay illegally during the long wait," but here's the problem.
Unless you become a U.S. citizen at some point before (or soon after) her wait is over (when it's time for her to put in her portion of the application for her green card), she won't be allowed to stay in the U.S. for the rest of the green card application process: She'll have to go to a U.S. consulate overseas. But once she's outside the U.S., a particularly harsh law kicks in -- this law says that once the consulate discovers that she has lived in the U.S. for more than a year illegally, she'll be barred from returning to the U.S. for another ten years. (And believe us, they'll make her prove exactly where she was for the last several years.) There's a waiver she can apply for (based on showing hardship to you), but it's extremely unlikely to be approved.
As you can see, this is highly complicated stuff. It will get much easier if you become a U.S. citizen, so be sure to see Nolo's articles on how to become one.
Still, there's much more to know about than we can tell you here, including the risks of being accused of fraud if you use a tourist visa to enter the U.S. and then get married. For much more detailed information, consult Nolo's Fiancé and Marriage Visas: A Couple's Guide to U.S. Immigration.