Like nearly all of the larger rental companies, Avis have a desk within the baggage reclaim section of Palma Airport. That way, if it is busy when you arrive, one of your party can get in the car-hire queue, whilst another waits for the bags to come off.
You don't say what day you are arriving, but if it is a Saturday in June, there will more-than-likely be a queue. PMI is a very busy airport, but either way, it will be quicker than being taken on a minibus to an off-site location.
If you allow an hour from collecting your bags to hitting the road, you should be fine - It is often much quicker. Avis cars are full of fuel, so you can head straight off, and you will be in PP within around 45 minutes.
If you are choosing Avis, I always go directly to their office in the car park directly opposite arrivals, as if you check-in at the desk in the terminal, you will be sent there to collect your car anyway.
Here is a link on Google Streetview (taken out of season - It is never really that empty!);
http://goo.gl/maps/okcML
When you collect your bags, just leave the terminal by the nearest doors. You will come into an area lined with tour coaches, and you just go straight ahead to the car park opposite. (Simply walk below the overhead walkway) There is a cafe in the entrance to the carpark, and if you turn left, the Avis office is ahead of you.
I don't know how big your party is, but be mindful that often it can be cheaper to have two Corsa-sized cars, than a larger people-carrier. It is also worth noting that Avis (and Sixt) don't charge for an additional driver - Especially handy if, like me, you can be easily tempted into an extra lunchtime drink....