I think it is a wonderful idea.........most women like to be asked at the place where they first met. It reminds them of how blessed they were to have met their future husbands.
Now are you asking at night? If not candles may be hard to see in the day time.........so you will want to consider using deeper candle holders with a colored theme so the light can shine against the holder.
One issue I see is she may find it odd that the friend is driving her to the bus stop and when she See's the flowers and candles she may know immediately what it is for. What I would suggest is getting rose petals (Real are better to prevent being ticketed for littering) and have him drop he off around the corner from the bus stop..........telliing her to follow the trail of petals. Which will lead her to the bus stop where you already are at with the puppy and flowers and the ring. This way when she is dropped off, she may not immediately associate that the bus stop is around the corner and it will be a immediate surprise when she sees you standing there.
As for the rings, no you will only get her the ring. Once you get the yes, and are planning the marriage you will get her a wedding band (Make sure you pick up a ring which has a matching band that you can purchase now or later) and then you will get your wedding band before the wedding.