If you want something specific for a coffee shop, and less intense than Steve Mayeda's approach, here's a few things you might like.
1. Draw a tic-tac-toe board, write an X in it, and place it on the table. When she figures out what it is, put a pen in front of her.
2. Tip a barista to bring her a drink.
3. Write down the title of what she's reading, draw a dash, then write "you like it?" after the dash.
4. Throw her a paper airplane with "you're beautiful--but can you fly an airplane?" on it.
5. Put a sticker on her hand, see where it goes.
The biggest problem you're having is a feeling that you lack permission to open. That'll make opening an anxious proposition. A few tips for overcoming this. Most important, sit close. If you can sit close, conversation is likely to happen organically. After it does, be sure to ask her opinion on dating in Dallas. That'll steer the conversation to a place where you can ask her out.
If you can't sit close, and none of the five suggestions above seem right, remind yourself that charisma and charity are like principles. Giving her a fun story she can tell is a charismatic act as much as it's a generous one. Remember: 99% of approaches she gets are from the 1% of assholes that have a taking mentality. Lastly, most girls have a guy that they like, a boyfriend, no time for a relationship, or a ready "no" answer for some other reason. That means nothing for you. If she likes you, she'll find a way to say yes regardless of her status. Kindness is a rarity in romantic relationships, and she'll honor your efforts to bring some fun to her routine.
If that raises any questions on your part, ask away