UK student, fiance is in USA

1) I am doing my master's in England right now (US citizen). Fiance and I are planning a wedding in Mexico (he is a citizen there but has permanent residence in US) for this December (2013). Most likely I will stay on to do my PhD in England, so I will still be living here. If we are married in Mexico does he have to return to the USA to apply for a spouse visa or would he stay in his home country to do that?

2) I have seen several threads say that he would be able to work on a spouse visa (please correct if I'm wrong). What about if he has a fiance visa (he's thinking of coming in August)? What can you "do" with a fiance visa vs. a visitors visa?

3) Is it necessary for him to come here on a fiance visa prior to coming as a spouse?

What's your nationality?

US

I don't think you can sponsor him for a fiance or spousal visa as you yourself do not have permanent residence/citizenship.  See below for rules on bringing a dependent over:

From 4 July 2011, you cannot bring your dependants to the UK unless you are:

• sponsored by a higher education institution on a course at NQF level 7 or above which lasts 12 months or more; or
• a new government-sponsored student following a course which lasts longer than 6 months.

http://www.ukba.homeoffice.gov.uk/visas-immigration/studying/adult-students/family/

Yep, you'll need to get him a Tier 4 dependant visa.  Spouse and fiance visas are only for UK citizens or permanent residents. 

Ah okay, and I'm betting he can't work on that?

Ah okay, and I'm betting he can't work on that?

Actually, I think he can, with a few minor restrictions.

Ok I will look into that more. Thanks!

Yes, he can work on a Tier 4 Dependent visa - I believe he can take any job he qualifies for (unless it's a job that requires him to be a UK citizen or permanent resident, such as certain government positions), and I'm pretty sure he can work as many hours as he likes.