you always have the right to say no to something you don't want to do in bed. but in personal experience, the longer you are with someone the more you will start to open up to new ideas. i don't give my boyfriend blowjobs because he says it makes him too self conscious (lol i know) but whenever i give him handjobs and he comes i've started licking it off my fingers

it's really not that bad. the taste is subtle, it's not unpleasant at all. like lele says though, the taste varies depending on his diet. you can't say you don't like the taste if you've never tasted it. try it and see lol. maybe you could try doing what i do, and lap it up in really small amounts so it's not so daunting.
don't let him come in your mouth just because he pesters you about it... do it because you want to! maybe in time you will open up to the idea. but if you don't, no worries. he will just have to learn to live with it!

a lot of women don't like swallowing and it is totally your choice.