Ok. Luckily, thanks to the Supreme Court knocking down DOMA, same sex marriages are available all over the U.S. A Vegas wedding would be nice! But it's entirely up to you. I will provide you a link so that you can see the different requirements available all over the U.S.:
You just pick the place that is most convenient to you and has the easier requirements.
As far as a green card, after you marry, you will need to file an adjustment package. This includes the following forms: I-130 (Petition for family member), I-485 (application for Lawful Permanent Residency), I-765 (Application for work permit), I-131 (Application for Advance Parole), G-325a (Biographic data - one for each of you), I-693 (Medical exam that a certified doctor must fill out), and I-864 (Affidavit of support). You will need to file each form with supporting evidence and appropriate filing fees. You can find these forms at www.uscis.gov/forms.
The supporting evidence that you would file would be birth certificates, marriage certificate, divorce certificates if either of you have been married previously, proof of your spouse's U.S. Citizenship, proof of your legal entry into the U.S., and financial documents of your spouse to prove their income over the last year at least.
In about 3 to 5 months after filing, the work permit and Advance Parole (travel permit) should be issued. About 5 to 7 months after filing the interview should be scheduled (though now it is taking longer, so maybe closer to 7 to 9 months). If all goes well, a few weeks later the U.S. Lawful Permanent Residency card (green card) should come in the mail.
Please let me know if you have any additional questions as I will be happy to respond, but because this case is the type of case that I love to handle, I will now send you a low-cost offer so that I can pass on my personal phone number and email. I cannot discuss pricing on an open forum, but if you accept, you will see I have multiple services available to you from document review to full representation and all at very reasonable prices. You won't be disappointed as these are my favorite cases to do and have been doing them for many years. If you decline, no problem, you can ask additional questions without any additional charge. But PLEASE remember to leave a positive rating for me. You can do that by clicking on the 3rd, 4th or 5th stars if you see them, or the smiley faces if you see them. Also, a bonus is always appreciated if you feel I earned it. And finally, your question does NOT close just because you leave a positive rating. I can still answer additional questions for you without additional charge. Thank you for your understanding.