In the wedding scene at the beginning of the movie, all of the guests at the wedding rise when the bride is about to go down the aisle. Two girls, who happen to be sitting, notice Mary. Everyone around the girls are sitting also. In the next shot, everyone in the church is standing because the bride is going down the aisle.
In the park, there's a tight shot of Dr. Edison flicking all the "non-brown" M&Ms out of his hand but when he explains why he's doing it his hand continues to move. Then when it cuts back to a medium shot, colored M&Ms are back in his hand.
When Steve rescues Mary from the dumpster, they fall to the ground and Steve catches her head with his left hand. In the next few shots, his hand jumps from underneath her head to a hand either side of her head.
A taxi journey from the Golden Gate Park to City Hall would not go via the Presidio. It's clearly more dramatic for the movie if they get stuck in a traffic jam with a beautiful background, but there is a much shorter way to get to city hall.
After the dance lesson when Fran says Eddie will have to take off work on Friday to go inspect the vineyard as a possible wedding site, he says he can't because he has a diverticulitis seminar. It would be highly unlikely that he would be attending such as seminar if he was a pediatrician since diverticular disease is uncommon before the age of forty.
After Steve saves Mary and Mary's subsequent hospital stay,Steve tells Mary that he only treats pediatric patients. In the same scene, Steve checks Mary's blood pressure with an adult blood pressure cuff when a pediatric pressure cuff should be the norm, as it is a children's hospital. However it is a hospital and of course would have adult equipment around. A child's arm cuff would not work properly on an adult arm.
If Mary is a professional wedding planner who read the Donnelly engagement announcement and was going after the account, there is no way that she would not have known the full name of the groom, not to mention the fact that he is a doctor, regardless of the nickname Fran used for her fiancé.
After Mary and Steve knock the statue over, they lift it back into place far too easily for the limestone it's supposed to be made of. It also makes a hollow sound, as though made of fiberglass or plastic.