Depending on where you are going to be living for the next few years, you should speak with an immigration attorney to discuss the pros and cons of filing an application with USCIS upon marriage. If you do, then your spouse will receive permanent residence which will be valid for 2 years (if you are married for less than 2 years once the application is approved). Then, your spouse will have to remove the conditions, and only after three years will he/she be able to apply for US citizenship. However, there are certain residence requirements to apply for citizenship. Thus, if you do not intend on residing in the US, you may want to wait to file any application for him/her to ensure that he/she does not abandon his/her permanent resident status once he/she receives it.
There are many issues to consider when determining when to file an application for your spouse so that you can remain together in the US. I would recommend that you seek the advice of an immigration attorney to discuss the best process for your particular situation.