These types.. perfectly safe.
If you are in a warm southern state you are probably fine, otherwise I would suggest all solid walled cage with at least one element.. you have to consider your heat sources need to retain enough heat to warm the bottom half, so its a balance between heating, cage design and overall ambient temps in the area the reptile is at.
Ps plexi glass really sucks.. it gets bowed in short times, scratched up and looks distorted.. add to that high cost. When i made my last cage I picked up an el cheapo sliding glass door (or was it a big window).. worked great looked great etc. There are a LOT of contractors that resell or give away that sort of material.. I see the local dump workers ocassionally set them asside for people to repurpose