My boyfriend is working in the US as a nurse. While Im here working in Singapore under Spass.?

Unless your bf is a U.S. citizen, you should apply for your own green card to immigrate here permanently (permanent resident alien status). Once he is a citizen, you can marry and your status will be permanent as long as you remain married. You each can pursue both independently at the same time. It doesn't matter where you marry as long as it is a legal marriage in that country.

It is easy to get marry but it is not easy to apply for a green card in USA. It will take from 2-10 years to get a green card if you are not applying by marrying a US citizenship. Since your boyfriend is working in USA now, he can actually start applying his green card ASAP without wasting time. If you are in nursing, it is a career in demand in USA especially in California. So it will not be a problem for you to get a job once you are here. You can get marry anywhere in the world as long your marriage is genuine. But make sure you both register your marriage first before applying for your green card. Good luck!