Quick question:
I'm pretty good at C, C++, C#, Java and android developing in general.

How long would it take me to get semi-decent at ruby and ruby on rails? I can invest full time on it.

I searched quite a lot on google but I came up with 1 month to 2 years range, which is a bit too broad.

Thanks a ton.

That entirely depends on you and your dedication. Start today and you'll have a forum, blog or whatever by the night. Spend few more days and you should get all the basics. It took me about 3 days to fully grasp Golang and after a week I was really comfortable with it, but ruby has definitely more nuances to it. YMMV.

Thanks a ton for the kind reply and the examples!

If you have thorough understand of the above languages you've mentioned you can probably pick it up pretty quick. That said, you'll want to be read for the large syntactical change you'll notice with ruby (That with the lack of braces, etc).

You can find some great linda lessons on it too which can be found quite useful.