Yes, you should join a professional association, because belonging to one is a sign that you are engaged in a profession.
A profession can be defined as "a calling, vocation or employment requiring specialized knowledge and often intensive academic preparation." Besides a common body of knowledge, benchmarked performance standards and a code of ethics with enforcement, professionals are expected to have representative professional organizations which, among other things, ensure a minimum standard.
Professionals often form a recognizable community to ensure that competence is maintained and put to socially responsible uses.
Professional organizations advocate on behalf of their members
The role of a professional organization is not only to advocate on behalf of its members but to facilitate interactions among practitioners, educators and researchers via conferences, journals, websites, list serves and so on. Professional organizations communicate to many audiences that the represented professionals are competent, needed and guided by standards (i.e. ethical codes) that act to minimize or to prevent harm to the individuals they serve.
Professional organizations can be structured as an association or a college. Both organizations can coexist within the same profession and have very specific roles and functions.
Associations usually provide educational opportunities
The role of an association of professional members is to promote the profession and advocate for its members. An association usually provides professional development and educational opportunities such as annual national and provincial conferences. It also provides additional benefits such as professional liability (i.e. errors and emissions, general liability) insurance.
Professional colleges ensure the competency of professionals
The raison d'être of a college is to protect the public by ensuring the competency of professionals. Colleges typically register and certify professionals through a rigorous application and examination process. A college registry of professionals is searchable and available to the public.
An example of a professional association and college coexisting within a profession can be seen in Vocational Rehabilitation. The Vocational Rehabilitation Association of Canada (VRA Canada) functions as an association and the College of Vocational Rehabilitation Professionals (CVRP) functions as a college. Many vocational professionals in Canada belong to both organizations.
Phillip W. Boswell, MA, B.Ed, ABVE/F, MCVP, RRP. . .