It looks like none of them were sent through the postal service. The one that has a letter written and addressed may have but I doubt given the fact that there is no marking other than the writer putting air mail on it.
I don't know much about postcards. What specifically would you like to know?
Again, per comments given in your previous post, the second card is a real photo type, commercially made. Once upon a time, most anyone could buy a camera that would take photos in postcard format and have them printed on card stock. So those cards are fairly unique and well sought after, assuming the subject is of interest. Commercial views can be good for accurate historic images but this is a rather stock/common type of image from Ceylon (now Sri Lanka). But, it's no wonder why: rubber and tea were major products from that country.
The third and fourth cards are linen-finish types; note the cloth-like woven surface pattern. Very common style from around the 1930s to around the 1960s, at least.
The La Fonda Hotel was once a Harvey House, a chain of hotels and restaurants owned by ATSF (Sante Fe Railway). Trains would stop here and passengers would be given a meal break here (and elsewhere), with large dining rooms and enough staff to take care of the crowd arriving all at once.
The Ohio Caverns postcard is neat. I have been there before, and is great if any has not visited before. Note there is over 100, 44 down to start and 60 steps at the end of the tour to get you back up to ground level.