Cloud computing has become an important research subject in software engineering. Among the many research gaps related to this new computing model is the lack of portability between cloud platforms, which generates the Lock-In problem. The Lock-In is the difficulty in migrating data and applications from a cloud platform to another. Current attempts to address this problem revolve around standardization of APIs and frameworks. We propose a different path, using model-driven engineering (MDE). We selected two cloud platforms and built a DSL and a set of automated transformations that generate code for each platform, based on a single portable model. We present the results of two studies. In a first study, subjects were asked to use the two versions of the same application, each one generated for a different platform from a single model. The subjects did not notice any difference between the two versions in terms of functionality. In a second study, we observed that besides facilitating cloud portability, MDE can increase productivity and reusability. These results indicate that MDE may be an alternative to standardization, not only helping to solve portability problems but also leading to additional benefits.