Sign up for part-time classes at the Arabic School of Portland. If you're a young student who hasn't completed high school yet, you can take classes on Arabic reading and literature, the Quran and general Islamic studies. Learning about the religion and culture of most Arabic-speaking peoples will help you more quickly digest the language.
Apply to study at the University of Portland or Portland State University. The former offers Arabic as a minor, while Portland State offers it as a full, four-year undergraduate major. Or, if you prefer, you could just sign up to take part-time classes on basic Arabic dialect, conversation and grammar.
Seek the assistance of a private Arabic tutor. You can browse advertisements on a website such as craigslist.org or view the classified ads in local newspapers like "The Oregonian" or "The Portland Press Herald." If you cannot find anyone offering Arabic language services, then consider posting an advertisement that clearly explains that you're looking for a private consultant or tutor. Offer a reasonable price and provide details on how much, if any, previous experience you have with Arabic.
Register at Listen & Learn USA. Based in the Township of Washington, New Jersey, this company provides language services and classes to students from all across the country. In particular, they host group classes on Arabic. The benefit of working in a group is that you'll have peers to help you in the process.
Attend meetings at an English-speaking Arabic church such as the Arabic Christian Church on 5000 SE Lincoln St. It'll give you an opportunity to meet and speak with Arab and Muslim individuals who also speak English. You may be able to make good friends or find someone interested in teaching you more about the culture and language.
Visit the Arab American Culture Center of Oregon. They don't offer any Arabic classes, but they do specialize in preserving Arabic culture in the Portland area. As such, they may be able to provide you with solid leads. Plus, they host many activities in which you could meet Arab people and learn more about them and their culture.