"Excuse me, how many of you?"
I had understood that 'ji' is for smaller numbers, whereas 'duo shao' is for greater numbers. Now when you come to a restaurant, either the waiter can see with how many people you are if you are with a few, or they have to ask, if you are with many, which would make 'ji' less appropriate since it will be a large number. Could anyone let his light shine on this?
Although you may know, there is a difference that worth mentioning.
位 is a honorific equivalent of 個 - so they are not interchangeable, or you would have appeared rude or too formal. This sentence is typically used at the reception of a restaurant, where using 個 to refer to guests is normally not acceptable. In reverse, it is not appropriate to use 位 when you are counting people among your family and friends.