I'm also using CakePHP and deployed some Cake-based projects, although
now I'm using Rails on most of my web projects. CakePHP is largely
based on Ruby on Rails, so I don't think you'd have any trouble with
the structure of the framework. There's the models, views,
controllers, helpers, and routing in both (scrap the concept of
components in CakePHP, as it's a hindrance when using Rails). You
might have a bit of trouble though when it comes to differentiating
between the concepts of the model class in CakePHP and Rails. In
Cake, the model class acts more as a utility class than an actual model
class (your model data is returned as an array of values), while in
Ruby, it's the model AND utility class (your model data is the
instantiated model class).
As for the language, once you've grasped the structure, you'd have
little trouble in coding in Ruby, and if ever you run into trouble,
just google your problem coz' there's tons of information, tutorials,
q&a's and the whole shebang around the Rails worldwide community. Or
get yourself a copy of Programming Ruby and Agile Web Development with
Rails (you can get the book, but there's tons of CHM and PDF copies
floating around), and of course the Rails API
(http://delynnberry.com/projects/rails-chm-documentation/). These are
the three most important resources for Ruby on Rails, although at some
point you would find that the Rails API is worth more than Agile Web
Development with Rails book.
Six months is too long. If you're persistent, you could learn the Ruby
language structure in less than a week (I'd say 2-3 days, maybe 1 will
do). And in another week, you'd know how to create your Rails app.
Give it more time, and you could delve into the wonderful world of
Rails unit testing (yes, it's built-in, unlike in Cake, and the same
goes for the mailer), plugins, rake, Capistrano deployment, Ruby
metaprogramming and more. In less than a month, you have an app ready
Ruby is a great language, and Rails a great framework. So good luck
with the learning process. It ain't that hard.