Is there any free portal script out there that can be used to create a travel directory or worldwide restaurant review directory?
I do not know fee travel directory but i can advice you to visit http://www.phpholidays.com/ as one of the best travel portal script but it's not free.
I would suggest you to install Wordpress & customize the theme & install necessary review / rating plugins to create a travel or restaurant review website. There are lot of plugins & theme in Wordpress Repository to achieve what you wanted. All you need is to spare some time & explore the possibilities & invest time to do all these. If nothing works out , hire a freelancer to help you with it . Hope this helps