Simple answer: Yes.
A 'buyers rep agreement' means that you, the buyer, are hiring a realtor exclusively to show you available properties, representing you in the negotiations and sale of a property. Without it you have no representation. You are like a ship in a storm with no sale bouncing around in the wind and the waves not knowing if and when you will reach your destination safely. You may get there, but with a lot of bumps and bruises.
Simply put...choose a realtor, sign the agreement and find your home to lay your head in. You'll sleep better.