I use OKeyboard which is a small-sized keyboard unlike other keyboards that take up double digit mbs in space. OKeyboard is less than 1mb and the dictionary plugins are also code optimized which is the way to go now, not only storage space issues but efficiency and speed. I downloded OKeyboard, with English and Tagalog dictionary plugins PLUS Autotext/AutoNext (you'll want this awesome plugin !) and the total size of all app/plugins mentioned is still less than 1mb !!! So its fast when it needs to be fast and doesn't lack in features and highly highly configurable and customizable. I mainly use it for gesture and swiping (I set gesture sensitivity to 60%) features and it works great.
Another thing I discovered is that the Filipino dictionary plugin is the best I've come across. I can understand your gripe about having English and Filipino dictionaries separately yet want to make them both work together. Depending on what language you lean more to, use that dictionary and make it bilingual. This is what I did with OKeyboard (or some call it MultiLing Keyboard). Most probably like you, I'm more comfortable with English and then interspersed with Tagalog here and there then maybe later more Tagalog then back to English again. So I now use only English as it would indicate on the space bar of OKeyboard, but my User Dictionary is filled (!!) with Tagalog words from Aparri to Davao, from Boracay and back to Makati. If you can train your keyboard dictionary to accept this, do it. And with Autotext/AutoNext enabled in OKeyboard, I end up almost "picking" words from the suggestion bar most of the time rather than typing them. Come to think about it, as I realized, that I kept texting the same things, the same words, with almost anybody in my contact list over and over with only two main differences. The same words are used for ❶ friends and relatives and same words/terms for ❷ business contacts. I wish there was a bilingual dictionary for Filipinos (English and Filipino), but creating one for yourself is quite easy, surprisingly, as I found out using OKeyboard.
You will realize later that making your User Dictionary bilingual is the way to go to avoid any conflict with spell checker. It doesn't matter how aggressive your spell checker is so long as your User Dictionary has all the Tagalog words you frequently use. Though I have to mention no one really likes an aggressive spell checker. I actually disabled it in my phone.