I rode a landboard nearly every day for years on the beach in San Diego. Perfect for learning on those light but steady wind days. You can still learn all you need when it comes to flying and being pulled with a kite. Low altitude jumps, rolls, carves, toeside riding, etc are possible. I recommend using a large kite (I rode an 18M) which are slower and will support you somewhat if you fall. Just stick to a standard mountainboard with the standard tires, and hard pack sand (and hopefully not too many people on the beach).
However, once the wind is strong enough to be on water, get on the water! Strong wind, and small twitchy kites are not a good combination on land.