link_to flexibility

My website, user side, is just one controller/action

I reroute this:
http://www.mywebsite.com/:menu/:submenu

to this:
http://www.mywebsite.com/MyController/Index/:menu/:submenu

so that the visitors have a nice web url like this:

www.mywebsite.com/about_us/my_story

all menu and submenu is dynamically generate from a database, the
whole website is actually contained in the database...

the problem is that I don't know how to use the link_to helper in this situation

<%= link_to menu.name, {:controller => 'mycontroller', :action =>
'index', :menu => menu.name} %>

results in:

http://www.mywebsite.com/myController?menu=about_us_us

which works but sucks

I could do this, but I have to create a @site variable and set it everytime

<a href="<%= @site + menu.name %>"><%= menu.name %></a>

How would you solve the problem? Any idea, suggestion...
bye
Thanks

<a href="http://www.mywebsite.com/myController?menu=about_us_us "><%=
menu.name %></a>