It is possible. HOWEVER, calf and leg cramps are very common in general. ALS is very rare. Most calf and leg cramps are related to other things such as dehydration, electrolyte imbalance, stress, overuse of muscles, circulation problems, just to name a few.
To jump to the conclusion that calf or leg cramps in the absence of muscle function failure is ALS would be analogous to assuming that you have a brain tumor because you have a headache or stomach cancer because you have a stomach ache.
Please read the sticky at the top of this DIHALS forum to see when you should or should not be concerned about ALS.