i am pretty sure other guys will give you more refined and detailed advice to your question, but i will add my 2c.
before you keep thinking about doing mechatronics, i'd like to know what kind of companies in specific you are thinking of working for anyway.
you mentioned, money...and,
according to cornell CS survey, out of 24 who took the survey and were employed, roughly half of them were IT analysts/consultants hired by goldman, PwC, UBS, Lehman, and engineers hired by Microsoft.
http://www.engineering.cornell.edu/s...BS-ONLY-06.pdf
these types of companies (Microsoft, Google, Goldman, PwC) are the ones that's going to pay you the most if you graduate w/ CS degree...
anyway, if you are looking to be employed by those high-paying, "tier-1" companies hiring CS guys, i can hardly imagine them caring about your mechanical eng. skills at all