Community College or extension programs as a way of preparing for a Masters in Mathematics I wanted to get some directions on how to prepare for a MS Degree in Mathematics.

Background:


I'm interested in getting a Ph.D in Statistical Learning or related area in 5-6 years.
I took some courses in Mathematical Statistics and I struggled because I do not have recent coursework in Analysis, Measure theory, etc.
I studied electrical engineering with a very heavy mathematical component from a very decent University 20 years ago however, it is amazing how much I've forgotten.
I've always been fascinated by mathematics and I'm very tempted to build a solid foundation before partaking in doctoral study.
I am working at the moment - my job is flexible and I'm saving to take off a year or two for the final years of my doctoral work.
I have a couple of graduate degrees in the area of Computer Science and Artificial Intelligence


Plan:


I'd like to build up to where I was 20 years ago: calculus, linear algebra, diff equations, calculus of complex variables, frequency domain analysis.
I'd also like to take courses that are typically reserved for math majors like proofs, analysis, group theory, algebra, etc.

I think the best way to accomplish the plan would be a decent community college or extension program like (UC Berkeley extension) that offers online classes -- any recommendation?
I fear that not so many community colleges would offer the upper-division courses a math-major sort of person would want, especially to aim toward graduate school in mathematics. Further, you'd be needing letters of recommendation for grad school, and community colleges would not generate letters that would help you, since the letter writers (by far most often) would not be familiar with grad school from the side of mentoring and supervising grad students (even if they themselves did have a Ph.D.).

It is true that community colleges are usually much cheaper than "universities", but the coursework, context for coursework, and outlook of faculty teaching the upper-division courses you need, and their letters on your behalf, are things that you can't avoid but need.