The only way is to actually try it. Your neighbors may get good or bad speeds but that may have to do with their own home wiring. Check to see if your cables are RG-6, as that is the best cable for in-home cabling. Did the previous owner have a Docsis 3.0 compliant modem? As you can tell, there are many variables that affects signal quality and speed.
As trythisfirst said, get it installed and check for yourself. If it's true that the quality isn't good then you can cancel without fee, within 30 days of signup.