I want to be sure that I understand the situation correctly, you have client side validations applied, and would like to have a form element enabled/disabled when the page is reloaded or the form submitted? If this is the case you are going to have difficulty getting this in place, if you are only using client side validations the values will be lost when the page is reloaded.
If you are just trying to get one text field to appear and another to hide depending on the selection made you should take a look at this thread here:
In post 4 I have some step by step directions and an example page for this type of validation. Take a look and see if this will fit your needs. If not I could help advise on what may need to be modified if it needs to work differently.