Hey deepagmat82 - those are really good questions. EssaySnark says, it's never too late for anything! But at the same time, certain things are easier at certain ages, so we understand your concerns.
It's traditionally been much harder to make a big career change through any part-time program - in fact, used to be that many schools wouldn't even accept a P/T applicant who wanted to switch careers like this. Today though, a lot of the schools are becoming more flexible and more accommodating of different paths. This is a great question for you to ask of the schools themselves. Contact their part-time admissions office and see what they say. They will be able to give you some insights into how feasible it is, and how welcoming they are in particular for career-changers.
The biggest hiccup really is in terms of the post-MBA transition, and this often boils down to one area: Salary. If you've been working in Silicon Valley for a long time then you're probably raking in some dough.
Many consulting firms would be interested in you as a potential hire due to your experience (we presume) but at the same time, you're not going to be in the standard post-MBA job bracket when it comes to compensation. So that's the biggest wrinkle.
The other part of course is the nature of your current job and past experiences. If you've been solely an engineer all these years, it may be more difficult to make the pitch - you will need to show the adcoms how you're ready to tackle this new challenge based on what you bring to the table today.
In terms of programs: Typically a P/T candidate is limited by geography since they're holding down a full-time job. Berkeley has a great P/T program (called the EWMBA for Evenings & Weekend MBA) and we know of folks who've switched careers through that. UCLA has even more options for part-timers including a new hybrid / online option called the Flex MBA. These are both viable for you. If you're saying you would relocate for a P/T program (and somehow be transferred by your job?) then Chicago Booth is one to consider.
Hope this helps as you tackle your research for the right school and right program.
tl;dr: Yes you can change from engineering -> mgmt consulting through a P/T MBA but it's got some challenges, both in landing the job, and even in initially getting into a good school.
EssaySnark