Know Your Requirement
You must know that you need bilinguals from a particular ethnic background and they should have expertise in that particular field of work. This will direct your search in the right direction from the very start. You should have data of demographics of your customers as this will be your primary reason for adding bilinguals to your work force.
Post Ads in the Right Places
You will post the ads in the regular newspapers which are generally the company policy but you must also post them in places where you are likely going to get an even better response. Places such as restaurants in a given community that serve ethnic foods, grocery stores and foreign language local newspapers are all good avenues to generate interest.
Check Resources at Hand
You may have the bilingual person you are looking for inside your organisation. You may well have a qualified person who can speak the language of your liking. This can be useful as the person will be familiar with the working of the organisation and what is expected of him and will be well trained as per the needs of the company.
Engage Recruiting Agencies
You should also engage the services of a recruiting agency as they get resumes of all kinds and can find the right candidate for you. They may charge for their services but it is one way to find a reliable person without taking a headache for it. You can also be a member of bilingual chamber of commerce and can be in touch with resources at hand through that route.