I was in Varadero and did some fishing in December. I was also there three years ago and fished then as well.
There aere no charter companies for fishing in Cuba as all of the boats are gov't owned. The only way to book a fishing trip is through your tour operator at your resort.
Both times it has cost just under $300 for four people for about 5 or 6 hours of fishing. The fishing boats that they send you on are really nice (most are Italian made 25-35' boats). The guides are hit and miss as to wether they speak english, but who cares anyways, your only fishing
When I went in December it was really slow, I landed the only fish for our boat and it was a small Barracuda (maybe 15lbs). When I went 3 years ago, we caught a 35lb Barracuda and a 20lb Snapper. But there are Wahoo and Marlin out in the water there as well, but I have not been that lucky.
Here is a pic...