Getting checked out in a PA28 doesn't rob you from your (legal or practical) ability to fly a C152. If you school has multiple aircraft types, good for them. If you make sure you are checked out on a reasonable sample of them you'll find that you get better availability, and the ability to choose the plane for the mission.
If you don't fly a lot (say less than 25 hours a year) and don't have a lot of hours, it's best to stick to about three different types maximum though.