Johio,
Essentially yes, that is what I would recommend. If I needed a ride at the last minute, I would ask at the establishment where I am and ask them if anyone is around to take me to where I needed to go. Or I would keep a list of numbers (as I do) of drivers I know.
If you are walking the road (and not on the new sidewalk on the beach road) and a taxi stops and beeps at you, chances are they are simply looking for a fare. The majority of the drivers are hardworking folks trying to make money just as we all do. But the problem as has been illustrated here is that you have no way of knowing for sure.
Locals in Negril do not just jump into just any taxi. They typically wait for a driver and vehicle they recognize. This becomes second nature when you have been using route taxis your whole life.
But as a tourist visiting the island, you do not have the luxury of years of experience of knowing who the good drivers are, who the not so good drivers are, who is just a bad driver (although the dents in the car tends to point them out) and who may up to no good.
In an email conversation I have been having, I asked a very simple question. Regarding the robbery that just occurred, what percentage of tourists coming to Negril do think would know that Lilliput is about 2 hours from Negril and they should never get in that taxi? Even more simply put, what percentage of tourists would actually notice the Lilliput route marking and know what it meant?
This number becomes very important if someone wants to recommend that tourists should take route taxis. I personally think the number is very small, so there is no way in good conscience I can recommend that tourists take route taxis when I feel the vast majority would not know what the Lilliput markings meant.
School children are taught how route taxis work when they are young so they learn not to get into taxis that are "wrong". But visitors to the island also do not have the luxury of growing up being taught the route taxi system.
So having the establishment find or call a driver for you is the first thing I would suggest if you dont already have a cellphone and list of drivers you can trust.
And as a sidenote to this, every Jamaican I have talked to about this said immediately that the taxi must be stolen as no Lilliput route driver would be trying to run routes in Negril...