Just don't actually add your text to the button in photoshop, and don't use jpeg for the final image as you'll get jpeg artifacts especially around text.
Text should superimposed by the system you are using in the end. Akin to using css backgrounds.
This way you will support the wave of hi-dpi displays, be able to easily support other languages and will make correcting text or labels so much easier in the future.
Both the button and text should, if possible, be recreated in CSS without any images at all. But if you have to use an image, you are right that the text shouldn't be a part of it.
Text should superimposed by the system you are using in the end. Akin to using css backgrounds.
This way you will support the wave of hi-dpi displays, be able to easily support other languages and will make correcting text or labels so much easier in the future.