Not necessarily, however keep in mind:
1) It looks like teenager talk. So if you want to sound like an adult and professional, avoid it.
2) So often people (especially people who are learning English) use wrong short forms, and when they do so, it looks quite silly.
3) Don't assume that the other person understands what you mean. Not everyone uses such forms, and they may have no clue about what you wrote. They may feel shy to ask, and so you end up making them uncomfortable.
And if they don't understand you, your writing is without purpose. So don't be offended if they don't answer you or misunderstand you.
4) It depends on your relationship with the person, and on that person's culture. Avoid it if you are not sure.
5) Normally there are word suggestions that pop up automatically as you type on your cell phone, and they are so easy to click on, so unless you are lacking those on your phone I think using such short forms is quite unjustified. To me it looks like lazy writing, and it does not make the person look good.
6) Typing to your friends is part of your English practice time, so why not make use of it to practice proper English?
7) Some short forms are short forms for insults or other offensive things, and of course using them is offensive.
But there are different views, and I am sure many teenagers think it is cool. You choose what group you want to belong to and how you want to be an example to others.