I do know who Sanders is, but apart from my interest in American politics generally, his brother and nephew are rather good local politicians in Oxfordshire (yes, really!) so there is a connection here.
I would prefer him as president to any of the other possibilities; indeed I would prefer him as PM of the UK to any of the existing possibilities here, so if American voters don't want him, can we have him?
But yes, most people here would only know about Hillary and Trump - and possibly some would have been aware of Jeb Bush - with regard to this election; and we would all ardently choose Hillary, or indeed anyone including a literal donkey, rather than Trump! Trump seems an absolute idiot, bigot and near-fascist, all at the same time, and as I've said, if he gets elected president, I'll believe there's no intelligent life on Earth, let alone anywhere else.
Almost all English people aware of American politics would oppose Trump, whatever their other political views. Even Nigel Farage criticized him for his extremism, and if you're too right-wing for Nigel Farage, you are seriously too right-wing.
One more view from a foreigner, which you can take or leave: We leftish Brits know quite a lot about having an unacceptably right-wing leader for our natural party, and many of us voted for smaller parties when Blair was leader, or fled into Clegg's arms only to be similarly disillusioned by him. Many of us just plain refused to vote for Blair. But would we have voted for Blair if the alternative was fascism? - YES, most of us would. As many of our neighbours in France were prepared to vote for moderate Conservatives to defeat LePen. I would vote - with a clothes-peg on my nose - for Blair against Trump or Cruz. I would vote for a dead rat against Trump or Cruz. This is coming from an anti-partisan-loyalty type who wouldn't vote Labour for 10 years because of Blair, yet places opposition to fascism above almost anything else. As I say, I can't tell others how to vote, even in my own country, let alone anywhere else, and you can take it or leave it: but in my opinion defeating the Republicans on this occasion trumps (no pun intended!) everything.