Actually, Digital Press does tell you the languages for some games.
Using Dracula - Resurrection as an example:
After you search for a game and get the results:
By clicking the name of the game under Title, you'll be taken to the game's description page:
The non-English serial numbers will be given under Description.
The English serial number will be given under Part Number.
Also, the Sony Index has the languages for some games:
http://www.sonyindex.com/Pages/PSone_PAL_Name.htm
Scroll down until you see the games list, then scroll to your right to see the languages.
If a game has M-5 or M-10, that means it's Multi-language, with the number indicating how many languages.
If you don't see an English version for that game listed, then chances are that English is one of the languages in the Multi-language copy.