Just got a 5wt fly outfit, BPS brand, nothing special. Is this a good all around fly rod size? I'm obviously not going to be catching any BEASTS on it, but want to know my limits.

Also, I have an older fly rod and dont know the weight of it, how can i tell?

5 weight is sorta a panfish, medium stream trout, small bass kinda weight. If you are specifically targeting larger bass, then most would recommend a 7 to 9 weight rig.

If you search the web on something like "selecting fly line weight" you'll come up with a bunch of hits for sites that discuss the various fly line weights and their applications.

On your older rod - is there any markings left on it? Do you know the manufacturer? Have you tried the manufacturers web site for info? (For instance, I just found that the Shakespeare web site has a listing of their old rods introduction dates...but unfortunately no line rating for the fly rod). I don't know of a way to determine the line rating of a rod by just looking at it. Perhaps one of the long-term fly fisherman will come by with some suggestions...

To know what the actual rod wt. is you need to measure it on the CCS scale. It will tell you what the rod is, not necessarily what it was labeled. (which is often not accurate)

http://www.common-cents.info/

A 5 wt. will work for panfish, bass trout and more but as stated, you may have your hands full with bigger bass or cover. Just use a little heavier leader and you'll get by ok. The biggest limitation is casting larger flies, not catching the fish. There is a guide down on the Tx coast guides for bull reds (bulls are over 28") and only uses a 4 wt.

Now having said all that, I prefer my 7wt.  ...lol  But I do occasionally break out the 2wt and 4 wt. for smaller bass.

Ditto on the fly rod and line weight.  It's not so critical for the size of the fish you are catching as it is the size/weight/bulk of the fly you are using and how far you want or need to cast it.  Naturally, a lighter weight system will generally cast lighter flies more delicately (for spooky and discerning fish) but over shorter distances while heavier rods/lines are better for getting distance and for casting heavier flies.

If all else fails, you could always spool up your existing flyline and leader and see how well the line loads on the back cast and and how well it unloads.  You can usually get some idea.  Usually, rods will handle line of one weight above and/or below it's own "weight" with reasonable (abeit not perfect) performance.