I really think the best way to propose is:
1) Manage to buy a ring, even though you are together most of the time.
2) Borrow a couple folding bikes from a cool guy that happens to have a few extra
3) Go on a trip to Europe, riding bikes/trains through Sicily, Italy, Monaco and France
4) Propose to her somewhere in the hills just outside of Florence
5) Then... Enjoy lots of good food/wine, ride said folders up Alpe d'Huez, see 2 TdF stages, etc.. all as a newly engaged couple.
Just sayin'