I have a sand substrate, but I don't leave the plants in their pots. I prefer the roots to be able to spread out properly.
If you want tall plants, go for Anubias
. There are a lot of different kinds, but they'll do well in low-nutrient, low-light environments. They may grow slowly, but hey, they grow slowly in optimum environments as well.
There are also some awesome low-light crypts you should have some success with.
On the other hand, upgrading the lighting would be my top choice, but mostly cuz I LOVE planted tanks, and higher light would provide way more opportunity to play. :D. The sand shouldn't pose any problems. I'll attach a recent pic of my heavily planted play sand tank for proof, not a single fake plant in there. It's 86 gallons with 3x 24" Coralife compact fluorescent 65 watt.