My gym doesn’t have a regular squat set, so is it better to use the curl bar for squats, smith machine, or the leg press?
leg press? curl bar squats are extremely uncomfortable at any weight remotely heavy. The smith machine straight up scares me w/ the limited range of movement. Any way you could ask them to purchase a squat rack or even donate one perhaps? i found a decent squat rack for $100 on craigslist.com. just a thought
Single split leg squats, lunges, or step ups with DBs; work your grip at the same time! 
Do you pay to go to this gym?
But to answer your question leg press then smith smith squats would be my order of preference.
As there is truly no equal substitute for squats, I would say do as much as is possible(i.e. leg press, ham curls, smith squats, step ups, curl bar squats, lung variotions)
In a previous post you mentioned that your gym has dumbbells, so try Dan John’s goblet squat.
[quote]arthursaxon wrote:
In a previous post you mentioned that your gym has dumbbells, so try Dan John’s goblet squat.
[/quote]
Seconded! It’ll help your form as well.
http://www.T-Nation.com/tmagnum/readTopic.do?id=1713046
Maybe give lumberjack squats a try as well.
Learn to clean a decent weight from the floor, then do front squats.
Use the smithy and leg press if you want to go heavy. They’re not the best choices but it’s better than nothing.
Zerchers from a preacher bench. That’s how I do it (I have the same problem), and it allows me to use more weight than any other method (ie. power clean to front squat).
[quote]scottiscool wrote:
Do you pay to go to this gym?
But to answer your question leg press then smith smith squats would be my order of preference. [/quote]
Me too and don’t entirely discount dumbbell squats where the weight is lowered to the ankles and you go deep, preferably on a platform. These are much heartier than some may think. Also barbell hacks which could probably be done with a non standard bar for a while by a beginner. However these can be tough on your shoulders and back if done wrong.