It is not recommended that a foreign national enter the United States on a tourist visa for purposes of marrying. Marriage simply is not the intended purpose of a tourist visa. The purpose of the B-2 Tourist Visa is to permit entry into the United States for tourism, visiting relatives or other intentions contemplated by the visa. The F-1 Fiancee Visa contemplates entry with the intention of marrying.
Notwithstanding the distinctions between these visas, couples have wed while the foreign national is in the United States on a tourist visa and they have obtained adjustment of status permitting the foreign spouse to remain. Pivotal in adjustment of status is the intention of the foreign national when he or she entered. The necessary elements of proof of intention are that the marriage is not a sham marriage and not planned at the time the tourist visa was applied for.
The typical scenario occurs when the foreigner enters the United States on a tourist visa with the intention of merely staying for a definite time with the intention of returning to their home country. After arriving in the United States the foreign national meets an American citizen or permanent resident of the opposite sex, a relationship develops and the couple marries. The citizen or permanent resident then applies for adjustment of status of their spouse.
A 30/60 day guideline is often used in a determination of the intent of the foreign national. If adjustment of status is sought within 30 days of arrival, there is a presumption that the marriage involved visa fraud. If the adjustment of status is sought within 60 days of arrival, the presumption becomes rebuttable. After 60 days appears to be in the safe zone unless of course evidence exists that the marriage is a sham or planned.
After getting married and applying for adjustment of status, the foreign national cannot leave the United States without advance parole or obtaining permanent residency. Were the foreign national to return to their home country, they will not be allowed to return to the United States while adjustment of status is pending. They would be required to await issuance of a spousal visa. On that basis alone, the F-1 Fiancee Visa might be the better road but if a foreign national married in the United States while on a tourist visa, a Las Vegas wedding chapel may carry more credibility than a church and a spontaneous spur of the moment wedding may be more valid than a planned wedding.