Neuroscience is very broad. We can't really answer your question without more specifics about what kind of neuroscience you want to do.
There are several converging reasons why neuroscience is generally believed to be a "growth area" right now.
1). People are living longer and as the population ages, a greater proportion are becoming affected by neurodegenerative disease, the most common being Alzheimer's and Parkinson's diseases.
2). Due to modern medicine more people are living with traumatic brain injury (TBI) than ever before. When previously victims of TBI would most often not survive, increasingly these people are physically recovering but having with lifelong neurological impairments. This is especially a problem for war veterans. US involvement in two foreign wars is functioning to dramatically increase the numbers of Americans with living with a TBI.
3). Brain-inspired computer vision, robotics and machine learning systems now routinely perform at state-of-the-art levels. Many computer scientists explicitly credit neuroscience as their inspiration.
4). Advances in noninvasive neuroimaging (fMRI, MEG, EEG etc) in conjunction with new pattern classification methods are leading to unprecedented possibilities for "read-out" from the human brain.
5). There has also been tremendous progress with invasive "intervention" methods recently. This is where molecular biology is useful. For one promising example see: "optogenetics"
6). Developmental disorders such as autism and schizophrenia are now seen as important research funding objectives by many key agencies.Of course, many more reasons as well!