I have a multiple-entry B-1/B-2 visa, issued last October, which does not expire for two more years. I first used this visa to enter the United States to visit friends and do some holiday shopping in December. While I was in the U.S., I met a friend of my cousin who is a U.S. citizen. We really hit it off, and got married at the end of January right before I flew home. I was careful to leave the U.S. before the end date on my I-94.
My spouse does want to file a green card petition for me at some point, but it is very expensive and we do not have the money yet. Since my B-1/B-2 is still good, can I just use this to visit my spouse in the meantime?
Possibly, but because of your marriage, this particular use of a B-1/B-2 will take more preparation than your first entry. It may be easier to have your spouse visit you in your country while you plan and save.
The B1/B2 visa is a "nonimmigrant" visa, meaning that it is intended for people who only plan to visit the United States temporarily. This visa is not meant for a person who intends to immigrate—that is, apply for permanent residence or a green card. The U.S. immigration authorities take a strict view of the purposes for which each visa may be used, and may penalize any attempt to use a visa for a "secret" purpose.
In order to travel on a B-1/B-2 visa, you must show that you do not have "immigrant intent." That is, you must convince officials that you do not plan to permanently move to the United States at this point in time. (For more information about this and other basic eligibility criteria for nonimmigrant visas, see U.S. Immigration Basics.)
When you were issued the visa last year, it was based on your personal circumstances at the time. Now, your personal circumstances have changed. Officials at the border or airport may assume that your intentions have changed as well. If you come to the U.S. to visit your spouse, they could assume you now intend to immigrate, perhaps by filing an adjustment of status application in the U.S. rather than waiting to apply for your immigrant visa at a U.S. consulate in your home country. In that case, they would cancel your B-1/B-2 visa and note your visa violation in your immigration record.
If you want to be able to continue to travel on the B-1/B-2, then you will need to bring with you strong evidence that you plan to continue living in your home country for now, and to ultimately apply for your immigrant visa there. For example, you may show (with copies of various documents) that you still have a job, a home, family, and personal property in your home country. If you cannot show such ties to your home country, you may be denied U.S. entry and the visa cancelled. This will make it much more difficult for you to ever return to the U.S. as a visitor or an immigrant.
Upon your next visit, you may also get questions about your speedy marriage from U.S. Customs and Border Protection (CBP). There is no rule against getting married while visiting on a B-1/B-2; however, the officers may suspect that you had already planned to marry when you first came to the U.S., and that you misrepresented your intentions. Such misrepresentation would make you inadmissible. Therefore, you should also bring evidence that the marriage was not pre-planned and that you were honest about your intentions when you first entered the United States.
For related information on this topic, read Risks of Entering the U.S. as a Tourist, Then Applying for Marriage-Based Green Card.