The key to getting everything to work in Application Architect is to select what language your want to work in before changing a caption. The forms in SalesLogix will than change languages based on the language you have set your browser to use (e.g.. Set Firefox to use "es" for Spanish and you will see your Spanish translations).
By default in Application Architect's toolbar you will see a field called Project Culture which is set to Invariant. If you change the Project Culture to "es" that will tell the system you are ready to enter in a Spanish translation. On the Account detail highlight the Account field and enter in the new caption for the Account field. Leave the Project Culture on "es" and update the captions for all of the fields, Navigation buttons and menus you want to translate. When you are done with your translations save all of your changes, rebuild your web platform and deploy.
Finally, when you are running SalesLogix if your browser is set to use English (en-us) you see the English captions. If you change your browser to run Spanish and do a browser refresh you see the Spanish captions. I tried this and it did work plus the date formats in SalesLogix changed to match the browser selection (en-uk showed dd/mm/yyyy).
For Firefox version 3.6.x you can choose your language selection by going to Tools - Options - Content tab and Choose button. Add the languages you want to test and make sure the language you want to see is on the top of the list..
For Internet Explorer version 8.x your can choose your language selection by going to Tools - Internet Options - Languages button. Add the languages you want to test and make sure the language you want to see is on the top of the list.