I just had another call about this. And, I am not sure how much success the callers have after attempting to pursue the path I steer them upon. BUT, my standard answer is:
"No, I don't rent signs. But, I have seen portable signs at rental companies. This would be the type of companies that rent backhoes or other similar equipment."
Will they rent them in your area? I don't know. But, if they want to charge you $150 or so per month, and you need the sign for 3-4 months, you may want to consider a purchase. And, if you do, give us a call at SignsSeen!