Would you buy a pair of speakers by just looking at the measured freq. response?

At the factory, frequency response is measured at very low volume level at a constant signal with the microphone placed in the optimum location. (+/- Xdb @ 1 watt, 1 meter).  It shows nothing of the character of the speaker when things really get going.

I'd be kinda like buying a car based on measured sound levels with a mic positioned at center console position going 30 mph on a pefectly flat surface.  Not much of an indicator of whether or not it has the potential to create a possible medical emergency for passengers over 70 when you stomp on the "gas", or try to impress seasoned auto-crossers during cornering, or test the effectiveness of shoulder harnesses when you lock up the brakes.   Or, whether it just gets you from Point A to Point B as quietly and comfortably as possible. 

You gotta listen to 'em.

I will tell you a great way to pick a speaker. Look for Canadian  built speakers that were designed in the national research  council s anecchoic chamber and decide if you want to buy a God awful  speaker or not. If you want an awful speaker pick one of those the higher the cost the worse the speaker  if you want a better speaker pick anything  else. By the way I am just telling it the way it is about our speaker industry.  There are a few good speakers made here but I have yet to listen  to a good speaker that was design in that chamber. 

As @erik_squires said, frequency response is but ONE measure that is important. Maybe not the most important one either. But yeah, I look at frequency response curves to see if a speaker is jacked up in a range I don’t enjoy or if they’ve added a bass bump to make up for not have great bass extension.

Sadly, many manufacturers in the mass consumer market don’t even publish a frequency response curve but only say meaningless ranges like 40Hz to 20KHz without even telling you the +/- dB levels in that range.

So "no" I’d definitely not buy speakers based on ONLY their frequency response curve.  Impedance is important too and knowing how low it can go and at what frequency can tell you if your amp is even capable of driving them well. 

Unless you were a very specialized collector, would you buy a car without driving it first?

Ha….