A friend of mine is engaged with a US citizen. I sort of have all the details, but if he gave them to me correctly...he entered with a 10 year visa and has a border crossing card. I believe he said his visa expired, but has been leaving and entering the US with his border crossing card. Once they get married, can his spouse file an I-130 and adjust in the US or will he have to leave the US to do his interview in Mexico?
If your friemd entered the country with a visa, he can file his I-130 and adjust status inthe United States. At the time of the interview, he may have to file a waiver for his overstaying period in the U.S. As soon as your friend file his application, he should not leave the country becasue his application will be denied because he left the country while his application is pending. In that case, your friend's case will be more complicated, takes more time, and he would have to deal with a waiver becasue he will be barred from coming back to the U.S. for a period of ten years.