Guys, it's really, really sweet that you would want to propose... But please, please do not do so unless it is ABSOLUTELY CLEAR that both of you want to get married. I would even go so far as to ask, "Would it be ok if I proposed to you soon?" You can work out some kind of compromise to allow for both a surprise and the absolute agreement that this is what you both want and are ready for. DO NOT propose after a fight or if you two have not been getting along.
As Love already pointed out, such a situation makes the woman feel obligated and manipulated, not happy, loved, or grateful.
When I was 18, my boyfriend did "all the right things"--he asked my father first. He bought a ring. He sprung it on me and proposed... in front of "everyone." The only thing he didn't do... was ask if I was really ready to get married.
I was 18 years old!! I hadn't even finished high school yet!!! I didn't jump with joy, I CRIED over being put into this situation in which I felt I had no choice. I eventually gave the ring back and broke off everything.
My family is of a very conservative Christian background and my father told me, "You should have never said yes if you weren't going to follow through with it." But if it's made into a big public spectacle that EVERYONE ELSE knows about except for you, or you have glimpses but don't know exactly when it's coming so that you could stop it (kind of like being thrown onto a train track and hearing the train but now knowing when it will hit), what else can you do but say yes in front of everyone? I also felt as if I couldn't trust him because "what other" life-changing things would he spring on me without really talking to me first?
It's kind of like if an unsaved person goes to a church, crusade, or conference and everyone is rallying around them to accept Jesus into their heart. It's a wonderful thing... But in that situation, how likely are they to say no, even if they're deathly uncomfortable and not ready?
I applaud anyone who is serious enough about someone to want to honor both God and the other person through marriage. But good communication is essential--and while the intent may be wonderful, unless both people are ready for and have the same answer when "the big moment comes"... A miscommunication of this magnitude is a horrible way to start a marriage.