You can not use an Internet Cafe to access the bookmarks, the Firefox Sync add-on is limited to synchronizing the data, it does not include an option to access the bookmarks online from any computer. There are other companies that offer online access to bookmarks such as Google Bookmarks and Delicious Bookmarks.

Xmarks may continue, but you may have to pay to use it, for details see http://blog.xmarks.com/?p=1945

Thanks for that info. At least I know now. I'll try the options you suggest.

Sync doesn't allow this because the data is encrypted by the client — in order to provide web access we'd need to be able to read your data (or hand it over to the FBI!) and we don't want to do that.

You don't need to be able to read our data to provide web access. You only provide a web client that replicates Firefox Sync functionality. All encryption/decryption can be relegated client-side. As soon as the browser downloads the web app, it only has to send and receive data in encrypted form.