The exact time and place of a proposal may be a surprise, but anyone who is actually ready to be married will know it's coming. You should have thoroughly discussed marriage, children, your expectations, your future goals, and worked out the financial details long before the actual proposal. If you haven't done this, then a proposal is an empty gesture at best, odds are you won't make it down the aisle. Also if he is going to spend the money on a ring, it only makes sense to let you choose it yourself, or at the very least browse with you so he knows exactly what you like and expect. You will not be happy if you let him guess.