What do you mean by the subtitle options display in English? If you mean that when you select from the subtitle menu which language you want, and you see "English" for all of them, you will have to do the following: At the same time that you load your movie into ConvertxtoDvd, load the subtitles as well. You'll see the movie title in the window. Click on the + sign in front of it, and you'll see the subtitle streams that you added. Click on that + sign and you'll see the actual subtitles themselves. However, the [ ] will show the default language, in your case, English. If this is what you want to change, click on the + sign of the subtitle track you want to change, and the new line will show a check mark in a square, plus some other info about the subtitle track. Highlight that checked info line and right click on it. Click on Change Renderer Settings. You'll get a script of the movie on yellow background. Close that script window. On the right hand side you'll see the little rectangular window showing the language it's in. Click that open, select Spanish. Click on the negative sign in the box in front of the Subtitle Stream line, and you're done.
Do that for every subtitle track you add. Then after you burn your movie, when you select the subtitle track, it'll show the language it's in, and not the default English.