Most armies deploy cavalry because they are fast and can engage enemy missile troops, skirmishers, war machines quickly or for a hard hitting unit with a high armour save.
Saurus Cavalry are not as great an advantage for a Lizardmen army because:-
- the army is fast moving anyway with cheap, fast skinks (both skirmishers and terradons) who can hit 'soft' targets. Saurus infantry are resilient anyway (T4, scaly skin - esp temple guard 5+) and good on the offensive.
Because of the above 2 factors the benefit of cavalry in a Lizardmen army is lessened.
Add to this that Cold One cavalry do not get +2 str on the charge but +1 because they have spears rather than lances and there is some justification for leaving them out of your army altogether.
As always in Warhammer Fantasy Battle games though, it very much depends on which enemy army you are facing.
If it is 'rich' in missile or Artillery troops (like all Elves, The Empire or Dwarfs) then you might need units to close the Battlefield gap and enter combat sooner.
If the enemy is likely to be coming for you, eg. Chaos, Skaven, Orcs and Goblins, Ogres and Bretonnians (and maybe High Elves and Tomb Kings) then you can probably safely ignore Cavalry. They won't be needed for attacking war machines, protecting flanks or for outmaneuvering because your skinks are capable of this. You would benefit more by bolstering the core units or taking additional combat heroes.
If you do take Cavalry to counter enemy missile troops be sure to equip them with the Sun Standard of Chotec so shots fired at them are at -1 to hit.
Also, because they cause fear, I would make the unit sufficient to outnumber enemy units if you do take them (so a unit strength of 20 or more, costing 350 pts - excluding standard bearer and musician - which you should probably add to the unit). This starts to make this unit prohibitably expensive.
All in all, unless you have a specific plan in mind which requires cavalry I'd recommend you leave them out of a 2000 pt Lizardmen Army. I would always include them in a 3000+ pt game for the added flexibility that cavalry can bring to your battle plans.
There is one further reason you might decide to include Saurus Cavalry...
...the figures are totally awesome ! Check these out (click to enlarge)...
