First, all signs point to yes. I really hope you get engaged!
I could have written this post (in fact I drafted a very similar post yesterday and decided not to post it until I got closer to when we leave). What helped me was thinking, “what happens if he doesn’t propose?”. I’d probably cry and it would probably be an ugly, messy cry and he would see it and feel bad. He would realize that I really want to get engaged and this wait is killing me. Your Boyfriend or Best Friend has thought about buying the ring, has the means to pay for it, loves you, and wants to see you happy. If it doesn’t happen now, it will happen. All signs point it happening. It could be that there is an amazing proposal waiting for you at a later date. When he sees how unhappy it makes you not to be engaged, it may spark him to propose sooner. But worst case isn’t that you won’t be engaged, it is that you won’t be engaged now.
But that is the worst case, which I really don’t think is going to happen. The best case is that you go, have an amazing trip, and get some sparkly jewelry. The advice I got was to live in the moment, have an amazing trip, and hope that it happens. Act as if it could happen any minute, so stay positive and happy. I know several guys who waited to propose because their GF’s were in bitchy moods (and a few who went along anyway), so try to stay bubbly and be yourself. And look pretty for pictures 🙂
If you are still insecure (I know I am), enlist help. Do you think he would ask your parents for your hand? If so, can you call them and ask them if they know if anything is up (in the I don’t want to ruin my vacation by getting my hopes up kind of way)? This would only work if they were honest with you and know you don’t do surprises well.
If you are flying, can you pay attention to how he is with his bag going through security? If you are going international and will have an expensive ring, the trick I am using is asking if he has anything he wants me to place in my bag so that I won’t have to declare or pay taxes on when I come back (this isn’t exactly the truth).
If you are truly open and this engagement is not supposed to be a surprise, can you be honest and say “I know we talked about getting engaged and I don’t want to deny you the opportunity to do it your way, but I also don’t want to ruin this trip thinking it is going to happen and it doesn’t. If I shouldn’t expect a ring by Valentine’s day, please let me know in advance so that I can have my pity party now and not when we are on the plane returning from the trip”?
Good luck and I hope to see a happy update soon!