you can try out the "include list method" from the old wiki page. Instead of RewriteRule to index.php, use a RewriteRule to info/index.php/$1
update: tested on my localhost
RewriteEngine On
# Removes index.php from ExpressionEngine URLs
RewriteCond $1 ^(blog|home|TemplateGroup|P[0-9]{2,8}) [NC]
RewriteCond $1 !\.(gif|jpe?g|png)$ [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ info/index.php?/$1 [L]
i would try-out several things on a local dev machine first. You have to test for site-index and site-url etc. so that {path=} variables still work, or otherwise you have set a custom global variable for {site_root} or something to use for urls in the blog. EE does have to know it's path to the main index.php for various actions (e.g. info/index.php?ACT=xx)
http://web.archive.org/web/20120831062016/http://expressionengine.com/wiki/Remove_index.php_From_URLs