Can I use 我的腿累了 for "My legs are tired"?
我的腿累了 is not as good as 我的腿好累
The former one seems to suggest your leg tires on its own accord and sounds unnatural, where the latter one just states that the legs are tired (a condition). As a comparison, 我的手累了 is quite normal, where the hand seems to be a more active body part.

While other alternatives have subtle differences:


我的腿无力  = My legs are weak. (Maybe from hunger)
我跑不动 = I can't run (Maybe need to catch a breath / or guy is too fat)
我的腿很酸 = My legs are sore. (Maybe from sitting too long in a wrong posture)