Revealing mistake: At "El Beachio," when Kevin and Perry order the two lovely ladies a drink, you can briefly see that the glasses are already nearly empty as the waiter gives them to the girls. Presumably, this was done because the girls are expected to nearly finish their drink in a couple of seconds before making a sharp exit due to the embarrassing fake phone call Candice just made. (00:27:35)
Revealing mistake: When the two are in the mall at the beginning walking towards the camera you can see a couple of people in the background watching the filming.
Revealing mistake: When Kevin and Perry get puked on in the nightclub by the first guy on the balcony, you can see the second guy with his hands round his mouth covering the equipment used to project the 'sick' for a few seconds before he pukes. (01:05:00)
Answer: In the UK, at the time of filming the Ford Focus was a very popular family car. Not sure if it was the most popular but its definately a stereotypical family car. So its use would have been to signify that Kev's street is in a typical suburban area.