I don't know why what I'm about to write hasn't been said yet, and I feel it's important enough to bring it up some two plus years after the original poster asked the question. For context, I'm a software developer as well, in my early 40s, and I lived in Boston for more than two decades -- it's where I made my career. In late 2013 I came out as the someone who, like you, doesn't fit traditional categories when it comes to gender (how gender was understood in the 70s & 80s had a lot to do with why it took me so long, but I digress.)
To answer your question, it is up to you to decide how to express yourself to the people around you, including to the people in your work place. At the end of the day, the people in your work place should have no say whatsoever (with some exceptions, none of which apply to software engineering) in how you dress, and they certainly have no say in how you identify. In fact, it's against the law in Massachusetts to discriminate on the basis of gender, and that law also directly refers to gender expression.
It's also inappropriate to discriminate during the hiring process. You are not obligated to disclose your gender or how you express it as a part of searching for employment.
I disagree strongly with the other answers that demand you discuss your gender with your fellow coworkers. Expecting someone who doesn't fall into traditional gender categories to "disclose" is just another example of bias -- I mean, disclose what? that you wear your clothes? Frankly, it's not your coworkers' business. If you feel it's appropriate to talk about it before you're hired, then you should definitely do that. If you don't feel it's appropriate, then don't. I have always found that employers just plain don't care.
All of this doesn't mean you won't find people who discriminate. It does sometimes feel like I have higher hurdles to jump than my fellow employees, though nobody has ever given me any grief directly. (In fact, in the few instances when gender has been brought up, it has been positive.) But, look, the people you want to work for aren't going to judge you based on your clothing; they're going to judge you on what you can do and how well you interact with your coworkers (esp. when you start moving past individual contributor roles, if you decide to go that route.) So, do your job well and reliably and stick to your guns.
You mentioned that you don't want to work for someone who discriminates any more than they want you there. (To remind: the basis for 'wanting you there' should be how well you do your job and nothing else.) I have nothing good to offer when it comes to finding the employers who won't discriminate, law or no -- it's a guessing game. But, one thing I've found is that the Northeast, at least, is open to people who don't fit traditional gender roles; this includes employers and fellow employees.
I hope you've found your place in the post-high-school world and that it's treating you well. For me, being able to live my life the way I see fit has been worth whatever little grief has come my way. (Understatement of the year, there. It's the best thing I have ever done for myself, ever.)
Make sure you know about this page, from the State of Massachusetts government: http://www.mass.gov/courts/case-legal-res/law-lib/laws-by-subj/about/transgender.html