Ask the teachers or the principal if there are a couple of Spanish speaking parents who are regular attendees at things or who volunteer regularly. Recruit them personally to help out at events. It'd be even better if you could recruit them to help LEAD, but you might be a year or so from that. What you want now is to diversify the faces of the people who are seen to be volunteers. The Spanish speaking parents in our school really liked to volunteer with someone they knew (let's face it, we all do), so if you can get a 'group' of people that would be good.
Many of the parents understood English just fine, but were very shy about speaking. So, we always looked to recruit these parents for activities where we specifically needed Spanish speakers. Selling school t-shirts? You'll sell a lot more if there are English and Spanish speaking parents behind the table.
Hire a translator to translate for your meetings. If you can afford the little headsets that would be best. Meetings take longer if you have to wait for translation, but my opinion is that translation is better than no translation.
Provide childcare. Many of the parents who are low income have to bring their children with them. Many of our parents were employed in industries where one parent was working in the evening or at night (restaurants, hotels, etc.).
Be OK with a bit of kid noise. The Spanish speaking parents in our group were not comfortable leaving their children in child care until they were about 3. Toddlers are cute, but noisy. Relax about it.
Don't charge dues. If you're an official PTA, you have to pay the national PTA org. Don't get this money from dues. Our group was actually a Parent-Teacher-Organization (PTO) because we didn't want to have to charge dues. There's a great website called PTOToday.
Find out what resources your district provides. Our district provides some very good training for parent leaders.
Make sure that you go around an introduce yourselves at every single meeting. If you don't, the new people won't come back. Have everyone who's attending introduce themselves. We usually just said our name and what grade our kids are in. It's OK if the Spanish speaking parents do it in Spanish.
Have an agenda and explain what you're doing when you're meeting. Give clear instructions for things that need to be done.
Recruit volunteers in person or via the phone. Most of our low income parents (many of whom were Spanish speaking) don't have regular internet access. Electronic communication works well with the middle/upper-middle class parents but if you're on a tight budget, computers and internet access come far after food and housing.
Publicize and communicate what you do. What is the PTA? What does it do? How can parents help?
Make your volunteer opportunities clearly defined and limited. If we say "we need 10 people to help with the plant sale" no one volunteers. If we say "we need 4 from 10-12 for organizing the plants. We need 3 people for each 2 hour shift from 12-6 hour where you help load the plants into their cars" we got volunteers. We got more when we said "we specifically need parents who can speak Spanish to help out the Spanish speaking parents."
I instituted an 'open' house for the first meeting -- we had tables and posters set up and parents could go around and see each of the activities that the PTO sponsored or needed (birthday lunch table, Passport club, art literacy, teacher appreciation, fundraising, volunteer background check). We had sign up sheets at each table where people could put down their name/number if they were interested in an activity. We gave parents a little form that they could have signed at each table. If they completed them all, we put their name in for a drawing for a prize. We provided cookies and drinks and it was good.
Set limited goals for your organization. What one or two things do you want to accomplish. It's great to have a vision, but building an organization takes time. Honestly, my goals were: To get all of the board members talking to each other, to diversify the group of people who came to meetings and who helped out, and to model that if you volunteer, you can step down after a year or 2.
Volunteering is not a life-long sentence. Too many organizations run with the help of 3-4 people who do everything. Then these people get burnt out. Then they begin to act like middle schoolers in a gossip fest and they turn more people off. My huge achievement was stopping that in its tracks. If someone had a problem, they could come to me. If they didn't tell me, I didn't know about (even if I heard about it 2nd hand). Either you've got the guts to address me directly or it's not important enough for me to worry about. It takes 2 to make drama.
Above all, be genuinely friendly when you greet parents. Look them in the eye. Say hello and welcome.