Certainly you can only two, and that is absolutely your choice. However, it would look much nicer to have your dentist make you four porcelain veneers for your four front teeth. Then all four teeth should match perfectly in color. Also, the shape and proportion would make them look the best and most natural too.One thing we oftentimes see in cosmetic dentistry is "next worst thing syndrome", whereby the patient only notices the worst things (in your case the front two teeth), but after that is solved (in your case with porcelain veneers), then the "next worst thing" then becomes the "worst thing". It would be much easier for you and give a better result if the four were all done at the same time, rather than two now, and then two later (if you later choose to do that).