More information is needed. Depending on why your fiance is in prison and how he entered the USA he may not be eligible to adjsust status. Secondly your fiance probablyhas an immigration hold in which case he will not be released. He will be transferred to an immigration detention center once released from prison. In this case he can only adjust or present a defense to removal to an immigration judge.
Before the court can consider whether to allow your fiance to adjust you must be married and have an approved Alien Relative Petition. It is very unlikely that the court will allow a continuance for you to get married and file an I-130 then wait until it is approved.
Whether your fiance will be entitled to bond from ICE or the Immigration Judge also depends on facts that you have not provided.
Probably. For him to sponsor you, he has to file an affidavit support and prove to the service that he can support you financaially.
Please note that THESE COMMENTS ARE NOT INTENDED AS LEGAL ADVICE and are for informational purposes only. This response is not intended to create any attorney-client relationship and is only based on the limited facts given. The response might change should additional facts be learned and should not be relied on as legal advice. It is recommended that you consult with an attorney who can properly assess the situation, as well as all pertinent facts, prior to taking any action based on the foregoing statements
The question isn't clear. Is the fiancee who is currently in prison the U.S. citizen or the foreign national? If the U.S. citizen, then there is the affidavit of support issue as pointed out by my colleague. There is also the question of what he was convicted of, because if it is a crime that falls under the Adam Walsh Act, he wouldn't be allowed to petition for a foreign national.
This reply is intended only as general information and does not constitute legal advice in any particular case. This reply does not create an attorney/client relationship.