Short answer, yes. You will not have a problem using Malaysian cellular internet for Google Maps, e-mail, web browsing, etc.
Longer answer, the mobile networks are reliable enough that you should be able to use a prepaid cell phone for voice and data in most areas. Just like many countries, there are places you will not get reception such as jungles and other sparsely populated areas. Even urban areas have dead zones, in Malaysia and in other countries. Additionally, different carriers have different coverage.
Georgetown is a reasonably well developed area. You should be good.