When you enter the U.S. as a tourist you declare that you have no intent to immigrate. If you marry and attempt to adjust your status, you're doing just that - attempting to immigrate. Your thus run the risk that the USCIS will investigate your case for possible fraudulent misrepresentation upon entry (something that can get you banned from the U.S. for life) - and you've already drawn the attention of the USCIS.
If you want to go with a quick marriage and adjustment of status, I suggest consulting an immigration lawyer with the details of your case. To play it safe, unless advised otherwise by my lawyer, I would personally go with a fiancée or spouse visa, even if it means some amount of separation.

