The picture you used is not one of mine; Shai's?

I hope you're not changing any main letter placements from Colemak because then this can be a suggestion for Portuguese Colemak and not just some "Bee-mak" thingy. For Portuguese, the high frequency of the letter A (and the low H frequency) will be a contraindication to that, but I'd think that you type some English anyway so it evens out somewhat. I'm Norwegian so I know a bit about writing another language with different frequencies and I think it's mostly okay. The biggest issue for me may be a few of the digraphs actually.

Then you'll need to put in the special signs. However, the ç is so rare that I'm thinking it could well be placed on an "AltGr" key really? If not, then it could do well on the right-hand side. See my article on modding keyboards in the Technical forum, there you'll see how we've done it with the Norwegian ÆØÅ letters.

If you use Windows, I can help you make a Portuguese Colemak installation based on the Colemak but with the typical Portuguese glyphs more accessible.

Which operating system are you using? If it's Windows XP/Vista or a Mac system, then installing new layouts and switching between them can be made very simple and done without restart. The system allows you to switch between layouts using hotkeys if you want to.

Research tools for keyboard layouts usually require you to do a bit of programming to define your layout suggestion; they're fairly rough. Shai has used a lot of parameters together with his experience and knowledge about layouts, and I at least think that he's done an impressive amount of work. He says that he probably has spent around 1,000 hours working on Colemak all things considered, just so you get an impression of how much work it can be to get something really good.

Are you sure you don't type more English than you think? This board isn't an email for example.  ;)