It`s not last island to visit in general. 90% of time reha map is found on elon, and by that time you should have enough lds to take interesting army, so when you get to elon and find reha map go there and get as much lizardemen as possible, then return to elon and have fun with them (you`ll have elon, nameless, shetera, reha left to clear, maybe uzala) so plenty of time to enjoy lizard race.
As for not using them, who said that ? They next to humans with high moral build (take tirex and scaly bracelet and +3 moral to lizards, among easiest way to max moral to 1 race), and build that is most common with them : gorgul, gorguana, brontor/(paladin), chosha/highterrant and tirex. In red sands mod there are more lizard units so more builds available.
But as Sir Whiskers said if you want them before that time, try to find `all troops on debir` and instal it, there you`ll have all races on first island available and ready to use. Only problem here is that you`ll have enough lds to take only few and have to go back to restock your army often.
Have fun
